SHALL I WRITE MY EX A LETTER, IM DEPRESSED AND MY LIFES FULL OF **** HELP?

Its been 2 months and a half since we completely finished. I think im depressed , i lost my sister in my teens and then began a path of destruction, i was a "good girl" and lost myself. This last relationship left me cheated on at the beggining then date d at my boyfriends houseparty, i was spiked but i only remember small parts of the night , like crying and my boyfriend ignoring me when i asked him to help me because i didnt feel good, but apparently i was pretty ****** up and my boyfriends cousin and friends had locked me in a room and his cousin had with me, other things were made up but untrue apparently, my boyfried blamed me and split up with me. im scared of being alone and so his bestfriend was taking me out and cheering me up and we got along well, he told me he's broken up with his girlfriend (which was a lie) and said we'd be good together (which was a lie too) we had twice but unexpectedly my ex wanted to "give me a second chance" I wanted him back and kept me and his friend a secret and stopped what was going on but around two months after the events his bestfriend's "ex-girlfriend" read through his text and saw one to me and told my boyfriend who then asked me about it. I told him everything and now we have stopped all contact i don't talk to him or anyone but i wish i could write him a letter or something im in so much pain and i can't cope. I saw my boyfriends new girl, she was at the party so were a number of other girls he'd being seeing behind my back but regardless and I know im being a stupid, selfish *****, i just want him to feel a little sympathy for me. Shall i message him or his friend to say how im feeling i just want to be cared for it would be easy to die.