Edit: i forgot to use a question mark in the title, i'm sorry!

i wanna thank you if you consider taking the time to help me out with this first of all, it's such an over used topic and frankly to me it scratches on the surface my pride to admit or try to admit (annnnd what just popped in my head- i'm sorry for any grammer mistakes but i'm kind of wound up and not english so i hope there won't be any hard hits in regards of my spelling)
basically about 5 months ago now i got dumped (what was said was that 'we don't see eachother enough' and that is a pretty lame excuse in my head) consdering it was the first time i got dumped (we never talked again) but not only that, after less than a day he had a new girl and eversince has been whining about wanting to be with her someone he liked a lot who'm i knew about i guess but because i always assured that it won't affect 'us' i tried to have faith in him, ever since then i am constanly thinking about what happend and i can't stop to torture myself with it all day -seriously all dam n day. 
now sometimes it will feel like i'm over it but my unability to let other/new people close and my betrayed trust keep pulling me back, it's hard 
now my question: do you know what i mean when  i say 'obsess' (i will call it that just cause after 5 months i feel like i should have stopped bothering by now) over something like that? and how do you snap out of it? how do you deal with repeating thoughts and feeling used/wasted/angry because of someone elses actions? because i don't know how to deal with the anger that i feel when i hear about how he's doing knowing what he did and why (basically i got dumped cause he wanted to be avaliable for her after i put a lot of effort, time and a bit of my heart into making it work- now back to my ego that's why i said 'a bit of my heart' i dont even wanna admit that i'm hurt pshhh fuck that) i am currently in therapy but i'm yet too embarrassed to admit what i'm going trough still -in a serious way so my therapist would be aware of how important it is to me -so i hoped someone could help me out