Hi Lulu - well, you're right, I know exactly where you're coming from on this one. Not sure I have good advice, you will probably get better from someone who's not fucked up like me, but I do have understanding and sympathy and all that kind of thing.
I could have done exactly what you did on many occasions. In fact I'm sure that I will end up doing something like this before too long as I can feel it all building up inside at the moment.
I think the need for reassurance and essentially confidence-boosting is an almost inevitable product of being in an abusive relationship. With that type of relationship, all your boundaries and standards of normal behaviour get so bent out of shape that it's difficult later on to know what's okay and what isn't. And it's horribly difficult to believe that someone actually loves you and wants you for yourself. I have a huge thing going on with LM that I hope and pray he doesn't know about, but probably does, about whether he likes me or not, whether he really wants to be with me or just feels he ought to now I'm his gf, whether he's still in love with his ex, whether he actually fancies me blah blah blah. In my heart I just want constant reassurance, constant contact, don't think I would mind one of the fifty texts a day guys that everyone else gets peed off with as I'd know he was bothered then.
So what I'm trying to say is that I don't think the need for reassurance about everything under the sun is something to be surprised at. It all comes down to self-esteem and self-confidence being destroyed over years and years of abuse and controlling behaviour. And however hard we try, that's not going to come back overnight. You read so many posts on here saying "work on your self-esteem" but I don't actually know how to do that. Maybe at your next counselling session it might be worth mentioning?
Anyway, none of that helps the current situation. In a way, it must be a relief that he actually knows everything now, how you feel deep down and how your last relationship has affected you. I don't think that he is going to finish things because of one drunken evening, I really don't. Things have been going so well between you and you're now at what is possibly a difficult stage of a newish relationship, when you start to let the "real you" show a bit more and become a more rounded person rather than someone who's always on their best behaviour and trying to present the best image all the time. He will be doing the same too, though - maybe not as dramatically!
I'm not sure how much he knows about your counselling, your ex and associated issues. I might be tempted to send him an e-mail just saying sorry you got a bit drunk last night, you'd had counselling and it brought all sorts of things to the surface and although you didn't mean to give him a hard time you do feel insecure and it's something you are working on with your counsellor. Was he a bit drunk too as that never helps?
Sorry, this probably isn't much use, but please try not to worry too much as it's not the end of the world, it really isn't. If you are feeling a bit hungover as well, things always look a million times worse than they actually are. Be kind to yourself today, take it as easy as you can and do whatever it takes to stop going round and round in your head with all this. Easier said than done, but stay busy at work, clean the house, go to the gym, whatever.
It will all work out fine. ((((Hugs))))