How do you get it to stop?

i feel so pathetic, but i got out of a bad relationship about 3 yrs ago and i am in a new one now. but i am still trying to process what happened. there are times that i still feel really sad about what happened. in my eyes i thought our relationship was so fun and loving but at the same time i remember him being jerky. he was physically abusive once and i am still trying to figure out what happened. i get so sick of thinking about it and when i cant turn my brain off. i dont know what to do. its like sometimes i miss things we had but then i know i love the guy i am w. too. then there are days when i feel so stupid for even thinking i could miss this ******! what is going on with me? and how do i make it stop?