I (25f) have ALWAYS felt guilty of something. I can't remember a time of being free from guilt.

Presently I feel enormous guilt over two things. 

1. The messy breakup I had with my bf of 3 years.

2. I met a new guy but he was very wary of commitment so were "together" but not dating...or something. Things like that confuse me and I hated it and told him that.  During this time I was put on Welbutrin and just starting DBT.
I ended up sleeping with my ex once which I oddly don't feel bad about.  But i am overwhelmed with guilt over one night when I blacked out (I didn't realize that was a side effect since I just started the meds two weeks before) and slept with another guy. I told the guy I was seeig that I blacked out and it scared the hell out of me and something happened but didn't go into detail and didn't say sex.  He forgave it and I think we both realized we really wanted each other and were afraid to lose each other and we ended up becoming bf and gf shortly after. 

I feel like I should tell him everything but I feel like it would just hurt him and it was before our real relationship so I don't even know if it matters now. 

I want to know how to stop feeling guilty all the time for weird things (like not being guilty about ex but bring guilty about the other guy). Like what techniques people use. 
I hate thinking that I am capable of bad things but it always seems like in just the worst person in the world. 

This was a much needed vent even if no one responds.