The female orgasm is very different to the male orgasm, I think. And we have many different types of orgasm (just to confuse the matter lol)
I think perhaps your OH is having small orgasms... I describe orgasms as kind of like climbing up a big hill...the feelings get stronger and stronger...higher and higher... then bang - I'm tipped over the edge...I feel like I've taken a huge jump and I'm literally flying...swooping and soaring for several minutes before free-falling back to earth (with a big smile on my face!)
The strength of my orgasm really depends on HOW I'm tipped over the edge. If the same stimulation is continued until I'm there, I'll have a biggy, but if I'm almost there....teetering on the edge, then something changes...like pressure on my clit or G-Spot, or even if Mr Spider says something I'm not wanting him to say...then I'll feel like I'm just pushed over the edge and skidding down the other side - those kinds of orgasm are nice but weak and not as satisfying. I can also be there...almost but something will happen and the feelings just suddenly fizz out like a wet firework!
Her sensitivity issues may be because she's not wet enough so you're chaffing her..use lots of lube and be gentle. The clitoris is a very sensitive area and lots of women don't like direct stimulation. Use your fingers or a toy which has the speed turned down really low, use one of the patterns too rather than continuous buzz.
Get down there so you can see what you're doing too - many guys fumble away down there...not saying you do... but hey - getting familiar with your OH's bits can only be a good thing. Don't concentrate your touches on just her clit - touch, caress, stroke, lick the whole area. There's a kind of V-shaped area above the clit... the area where no hair grows, I find stroking that area stimulates my clit. I love the 'V' technique. Use two widely parted fingers...kind of forming the letter 'V', slide them down either side of her clit and labia until your fingertips reach her vagina, then maybe dip a finger a tiny bit inside her. Keep sliding your fingers up and down either side of her labia and clit hood, the clit hood will rub her clitoris kind of like your foreskin rubs against your glans - that will make me come as quickly as directly touching my clit.
If she feels she needs direct stimulation with fingers or a vibe but feels the sensitivity is too much... you can use the vibe or your fingers through knickers rather than on the bare clit, that really gets me going too! In a way, it feels kind of naughty and like I'm being seduced, and does help if I'm feeling very sensitive down there.
Just get to know her body, My Love. Touch and caress all of her down there... avoid her clit totally, stroke or lick or even gently pull her labia if they're big enough, whilst occasionally dipping your fingers in her vag..a little deeper each time - tease her - she will get aroused and I bet once you've dipped in slightly a few times she will start arching her back, trying to get your fingers in deeper by altering how she's laying - but don't let her, you stay in control...you decide how deep your fingers go. Stimulate the whole outside region of her vag and anus...until she is really wanting something inside her vag, begging you for it! Then maybe very gently stroke her clitoral hood, very gently run your fingers up and down it gradually increasing the pressure until her clit has grown and is visible and out of the hood. Don't touch it directly as it will be really really sensitive... keep wanking her clit with the hood or use the 'V' technique again. Don't stop until she comes... it may take a while but be patient.
Wow - better stop - this is turning into porno lol. Hope some of my suggestions help you, My love - when she comes big style she will know - if your fingers are inside you may feel her muscles spasms, especially if your fingers are deep, for me, the walls of my uterus, vagina, anus, actually my whole pelvic floor contact - I think I go deaf and blind during orgasm too lol. I'm lucky, I have strong, intense orgasms really quite easily though - but it does take practice to come like that with both Solo or with a good patient partner.