Thanks for all the replies guys. Cheating is cheating regardless of gender, I do agree, I think for me sex with a guy is something I always thought I'd experience before I got into a relationship I'd consider serious. I don't plan to cheat on her, or tell her, as both would destroy the relationship I think. As to her going for several bi/gay guys, one she doesn't know about, one was her first boyfriend back when she started high school and he came out by dumping her so it was more of a close friend thing than a boyfriend. Added to that, she's probably the unluckiest person I've ever met, and it's a small town, so most of the guys she's dated are from the same group of friends - the two I spoke about are actually screwing at the moment, I really don't want to know how she'll take it if someone spills it to her lol
I probably should see a shrink or something, but there's no way I can afford it, so that's out of the question. So I don't really know what I'm going to do... but I've got a lot to think about and some of the replies really helped. Thanks