I have ex girlfriend issues...

And I have with most guys I've dated. My last ex cheated on me with his ex, and the bf before that was obsessed with his ex from 6 years before me. So I'm having problems with my current bf (S) and his ex (L). They were together for some years, sounds like a tumultuous realtionship w/cheating, on her part at least. She was a stripper and she left S for some old guy who she then married and had kids with. S and L broke up 5 or 6 years back.

He and I met thru friends about 2 years ago and neither of us were available to date, so we became friends. We have a lot in common. I moved away from that city (6 hrs away) in June 2011, but kept in touch and visited him when I was in town for relatives.

Last fall, I was kinda seeing someone and when I visited S, he was giddy with excitement because he had just reconnected and had a passionate weekend w/ L- who is only now getting divorced.

Next visit (feb), we griped to each about how these respective romances had failed. I saw S again around Easter and we ended up sleeping together. We decided to see each other long distance, which has worked out all right. We text everyday and call a few times a week. I send him art in the mail and he sends me writings. When we started, we saw each other every 2 months; now its every 3 wks.

Here's the ex issues- I was on the phone with him in July and I was apologizing (again) for kissing a girl in front of him when I'd seen him in June (it was gay pride weekend and she was my very lonely, very drunk friend). He said (again) that it wasn't a big deal, and to illustrate, told me he had kissed L. He had apparently re-reconnected with her about a week after my visit. She came to his apt and he told he a bunch of nice things about me and she cried to him about her impending divorce and he kissed her. He said it was to comfort her and they didn't make out though she did try to seduce him. I started crying and S got very distressed and told me he would never kiss her again.

So I realize I'm stupid because I kissed someone as well, and he and I hadn't talked about being exclusive/ bf & gf until recently. But he still talks to her and sees her and he had told me at one point that he loves her, though he did say he couldn't be with her again.... But he said if he ever slept with her, I'd be the first to know, to which I replied that he ought to control himself long enough to end things with me first. There are other things, but I've given enough to go on, I think.

At this point, our relationship is pretty stable- I don't think he's doing anything hurtful behind my back and he treats me very well when I'm with him. He hasn't told me he loves me as of yet, but I know he cares and I wouldn't want to push him. He says he doesn't find me jealous, and S is probably the least jealous person I've known. I also feel he's incredibly perceptive, except in regard to L and how she affects me. I feel he's genuine. We talked last visit about the possibility of me moving back to the city in several months... I'm seeing him again in a week. I don't want to ruin this with my insecurities, but I do want to discuss boundaries with him so we're on the same page. Opinions? Help?