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...dead horse. So to speak.
I agree with the poster (or posters) who proposed that the BF has some serious psychological problems, beyond the normal obsessiveness that drives a lot of males when it comes to the past sex-lives of their girlfriends.
LW, this guy fucked-up, and unless you want to have to go through years of therapy with him to get him somewhat un-fucked-up, you'd be well-advised to move on to someone who has done some growing-up.
And if he won't even go to counseling with you, then it's time to start moving out, because he's a lost cause. I've been on both sides of this kind of thing, and I know whereof I speak -- even if I don't know shit about much else.
At the risk of sounding smug, find an older man who's been around. They're a lot less trouble in general, if they're real grown-ups.