overthinking it

i'm ashamed to confess that i made a mistake. about two months ago, my ex gf were giving me mixed messages as she wanted a threesome with me and her boyfriend and herself, which i was willing to do because i guess i still loved her, but she backed out while we were drinking and smoking pot, she gave me mixed messages and then backed out and didn't want to do it, but she gave the go ahead for her fiance to have sex with me, and he did. now we are not friends anymore which i don't care about because they are awful people. I just feel awful and angry at myself for allowing myself to have sex with this man, he is a horrible man and I hated him since i first met him, they both are manipulative and messes with my head and emotions. and he lies about everything and make stories about his past which i don't believe. and yet i still allowed myself to have sex with him, now i can't stop thinking about it and wishing it never happen. yet there is nothing i can do to change it, so i have to accept the fact that i did a stupid thing and regret it. i just hope it doesn't come back to bite me in the *** someday.

I hope you practiced safe sex. That is the most important thing. You cannot undo the past, but you can not engage in sex (or anything for that purpose) with that many again.