Why are you, a guy in his late 20s, dating and sleeping around with teenagers?

Because it's not illegal, and I like younger girls. M is a bit of a different case however.

Don't do this. Find her another flatshare, but do NOT let her move in with you. Apparently you can't think straight.

I was planning on letting her move in long before we screwed, I was literally just coming down to help her pack up her things actually.

Break up with your gf, help your friend's sister find a flatshare, and then focus on yourself in counseling.

Lol, why would I do that? That's a pretty dramatic solution, I just wanted to get this off my chest, I don't think there's anything wrong with me.

). I mean c'mon.... your gf "is letting you sleep with other women"? Would she do the same if she was as old as you and had more experience?

I think it's really more to do with my personality than anything else, I don't think it has to do with my age or my experience.