Me an my oh was very active untill a few weeks ago.. He can get a erection through play, touch ect but when it comes down to sex it becomes soft. Im trying to understand but im feeling very frustrated an un sexy or wanted...
What can i do to help? Now been 3 days no sex
Tell him not to worry and that it doesn't matter and you understand. Enjoy through play and touch with no pressure to have sex. He needs to feel unpressured and totally at ease. Just give hime time. The more patient you are, the better the outcome should be 
Whoa there. It's been 3 days. 3. You need to take a step back and think about the pressure your frustration is putting on him, because whatever the problem is that will be making it so much worse!
Not to beat around the bush, it's very self centred and selfish to assume that you are unwanted or not sexy. Yes, it is automatic to feel that way and I know it is hard to get away from it as I've been there too, but you can't make this problem be about you when it is in fact about him. He's the one who really needs reassurance, not you! If he can get it up while playing with you, he obviously still finds you attractive :)
Have you spoken calmly about it to him? As in away from the bedroom and away from any expectations? It could be anything that is affecting him, only he can tell you. As PlayNaked said, bringing playtime back to touching only and bringing him to orgasm without sex could help him relax back into it all. Positive assosiation and all that! You could explore mutual masturbation or oral sex together?
The more pressure you put on him the harder it will be (well actually it'll be softer) three days is nothing! Take the pressure off stop asking for sex, give massages have a bath together and cuddle. If he's worrying constantly that you want sex and he can't give you it it'll make it impossible for him to get hard.
Tell him it's fine, you can enjoy yourself without intercourse, why not just give him a blow job, he doesn't even have to cum he can stop you when he wants all you want is to pleasure him, as long as he's happy you're happy.
maybe he's just stressed at work. He'll get past it either way, give him time to relax
In addition to the excellent advice above, if you find that taking the pressure off doesn't help much with him going soft, maybe consider a cock ring? You say he can still get hard during foreplay, a cock ring will trap the blood in the penis and keep it harder for longer.
Its been happening for over a month but now to the point of 3 days an he wont come near me. We used to have a lot of sex ect, his answer tonight was he doesnt no why its never happened b4 :/ i just wish i new what it was. I was in a abusive relationship b4 so thats why i worry its me i dont mean to make it all about me.
You have to not make a big deal of it, there are many reasons it could be happening, as men get older they stop being able to go again and again, he may be stressed at work. But one things for sure this is stressing him out and it won't help, whether you're frustrated or not you can't show it, be relaxed tell him you can still have fun without him penetrating you and even if he does get an erection don't pressure him to enter you, just keep playing, the more he worries about losing it and disappointing you the more it will happen. And if it does happen don't make a big deal, kiss him and tell him he was amazing not even acknowledge that he went soft rather than cuming