Your story is not uncommon. In fact this is more normal in long term relationships than the other way around (getting more and more experimental and more "needy" as time goes on) So it would seem anyway. I have no proof, but so many people mention this scenario playing out in their relationships that it seems to be the norm.
There is a good reason for that. At first you cannot keep your hands off each other, in a stage of lust. You are not living together and that degree of seperation keeps your drive up, anticipating the next time you will be together. Its new, exciting and fresh. This is the stage where we just cannot get enough of the other.
Then time goes on and we fall in love, we learn more and more about each other (The myteries slowly vanish) we become content and comfortable, happy but this is a deeper and different stage of love. We still lust after our partners, but slowly life comes back into the focus, with things like careers, children and other committments filling our time and taking our energies.
It can be hard to keep up that intense and heated level of lust that we have at the beginning. It is not impossible. I have been with my guy for over 4 years now and am highly sexed too and yeah, I still feel that wanting, lusting just as much as I did at the start. Just like Pink Animal, we get more adventurous as time goes on and I am very lucky to have found someone who seems as interested as I am. However, even we have been through blips of time where things just lulled, or dropped and it was like "omg - is the honeymoon period over?" lol It came back.
But it only comes back with a fiery passion if both people involved are prepared to put in a little work. Real life is not like the movies. We have to keep fueling our fires of lust and love. This is one important point to remember. In long term relationships, we tend to take our partners for granted more. Not on purpose, just because everything is so familiar and we fall into routines.
Think back to the beginnings, when you used to have to sneak around at parents houses, grab every moment, it was hot, spontaneous etc. Then sex becomes a routine. In your case, it is expected on the weekends (The fact both of you initiate and want it says a huge amount. She is still interested and still wants sex with you of course) The problem is breaking these little habits.
The habits need to be broken for sex to be spontaneous or different and again I refer back to my point about you both needing to be on board with possible changes. If she is perfectly happy with sex on a saturday and doesnt want for more, then it would obviously be harder for you to make any spontaneous changes.
Now, from what I understood from your post, the nights you come home drunk and over confident, you give your woman multiple orgasms. Also, it seems when you do initiate sex at the weekend, she wants it. I don't know about anyone else but this SCREAMS volumes at me. Your woman is massively turned on, by a confident guy who comes in, takes the reins and "goes for it" (as you put it) If she is having multiple orgasms when you are in this confident mode, it seems she likes having you in control and making the moves.
Now the trick is to learn how to do this when sober. Communicating about sex can be tough, especially when it is not something you have done before and yes, opening yourself up like this leaves you vulnerable and open to negativity, but you know the old saying "Don't ask, don't get" right? and the million others that basically say that you have to take a risk, jump into the fire, because it is rare for your dreams or desires to just fall into your lap.
It is tough, but just reading what you said about your lady and your relationship, I do not think you are with a woman who does not want sex, I think you are with a woman who is inexperienced, which naturally will make her feel very uncomfortable about coming forward confidently. It could even be that she is not sure what she wants yet. Seriously, I have been sexually active for the past 15 years and highly sexed at that and I am STILL learning things about my sexuality. I think this lady would actually be relieved and secure in you taking the lead, leading her places, slowly and gently, but together.
I honestly do suggest finding the courage to lay yourself open and to talk. If I have learned anything from my past 15 years, it's that communicating is one of the most important things you can do to take your sex life from meh to oh yeah! I have been with a few partners who felt very shy about discussing sex, embarrassed about certain things, but because I am so open, including dicussing those embarrassing aspects, I have noticed my partners become more and more open. They followed my lead and hey, if I am not embarrassed to discuss all this, if I am not shy about talking about all of these issues, then why should they be...and they blossom. Its a partnership, but someone has to get the ball rolling.
If you feel like it is just too much to discuss at first, try writing each other letters. You could either write a big letter explaining everything you think and feel, or you could turn it into a game (Hey, lets write down ten things we wish we could experience during sex or "Lets write down 5 things that we don't like during sex) you could even write each other about your top 3 favourite sessions together and why they felt so good (and in doing this, pick up those hints about what drives her wild...is there a theme you detect? You could even play a game of truths through text while you are at work, where you each take turns to ask the other questions relating to sex. (Have you ever, would you ever, do you like it when, how would you feel if, Whats your favourite, etc etc)
I seriously recommend finding a way to ease the pressure of communicating about sex, by finding a fun and entertaining way to do it (like above) rather than a very uncomfortable, serious chat. It will take the pressure off and being able to write it down gives you both a degree of seperation. I imagine you would find it much easier to reply to a letter or a text, than to sit in front of each other, staring at each others faces, struggling to answer the questions. Sex should be fun and so talking about sex should be fun too. If you can find a way to turn the chats from serious and uncomfortable,into a giggle fest, you will find you both opening up more and more. Top tip: people open up more if you are prepared to be vulnerable in front of them. If you are prepared to admit things that make you feel like turning red. If they feel you are comfortable putting yourself out like that, they are more likely to feel the same with you.
During the chats, listen. Really really listen. Not just to what she says, but to what she doesn't say! It is all important to figuring out what her hot buttons are, what she reeeeally craves and what turns her off. When you have this knowledge, you can build on it together and experiment. Never stop experimenting. Make her feel comfortable with experimenting by making it fun, making it a giggle (There is something very different between watching a partner look nervous, and oh so serious as he is fiddling between your legs, like he is diffusing a bomb, and someone who is just a lot more relaxed, smiling, communicating and enjoying himself too) Confidence is very sexy, but it only comes with communication and feeling comfortable with one another. If you try to change your mindset slightly and accept sex is fun and natural, it might help you get over that initial bump of communicating and if you start slowly and build up gradually, I have no doubts your partner will also open up to this, because you make it seem fun and natural.
There are many things I find sexy in a guy, it might be different for your partner, but confidence (not arrogance - there is a line) is sexy, as is humour and someone who is relaxed and enjoying themselves. I also love intensity and by this I mean everything from the look in his eyes, to his noises, to the way he moves. The more turned on he is, the more I am. So maybe just letting go is what your lady wants. To see her man so overcome with lust he just wants her..NOW!
Anyway, shutting up now. Turning into a ramble. Good luck though!