Honest opinions Mibba, is dating a good friends ex bad??

Even when she's said it's fine...

Because that's the problem I'm kind of having at the moment. I feel really horrible about it and I really need your help, just see what you guys think..

So I went to a party this weekend and a guy I've kind of liked for a while now was there, we'll call him Cory. Oh and 'kind of' meaning I've always thought he was cute and have wanted to get to know him better for a while now, so like I haven't had a huge crush on him, ya know??

Cory's one of my best friends ex's, I didn't really know her (call her Jackie) when they were going out so it isn't weird like that, but when they went out the second time me and her were just becoming really good friends and she was really, really happy about so we used to share cutesy stories about guys, you know how girls do when things like that kind of thing is happening haha..

They broke up because they realized they can only be good friends. She wasn't upset about it , it was a mutual thing.

But anyway, at the party we were drinking and stuff so I got a little drunk and ended up with him. I don't make mistakes like that when I'm drunk, I don't just randomly start making out with guys. When I'm drunk I do things that I've wanted to do for ages and just not been brave enough to do, it's normally quite helpful - even if my friends don't see to think so...
So I know for sure that me getting him with him wasn't something I didn't want to do, so I don't regret it really. The only thing I feel bad about is Jackie.

I talked to her the next morning (she wasn't at the party though) and she told me it was absolutely fine, she was happy for me as long as I had fun etc and I just couldn't read if she actually meant it. It seemed like she did and normally I can sense those things, but I actually couldn't tell with her.

He text me and we talked, he told me that he likes me and has for a while, he just didn't know how to talk to me or get to know me. So there's a real possibility that things could progress, but I don't want to hurt Jackie :(

What do you guys think? Is it bad to date best friend's ex's? Should I just call it off with him? Should I talk to her some more? What do you think...

I tried stepping into her shoes and thinking what if one of my best friends got with one of my ex's but I just couldn't see it. Or maybe I just didn't care... but yeah I really don't know.

Has it happened to any of you before?
Help!?!?!

PS. There's another guy too. He makes things about a million times frickin confusing :( And another guy, but I don't like him. And the guy that I'll always like, but he's a jerk. And I'm getting sidetracked..

I just need someone to talk to before I explode..
D:

Gen
xx