Could use some supportive words rn

T • Single teen mama 🎀
So my ex and I have been off and on for a while, he always leaves me for other girls. Will randomly stop talking to me. Parties , drinks, & smokes weed. & apparently does Coke & pills as well. But me being me, I always took him back bc I loved him & wanted to HELP him & aside from all that, he treats me very bad:-/ I know so dumb of me to stay... 
Well as of yesterday I saw a post of another girl kissing him, a girl that does all the stuff he does, drinks, smokes.. You know..
I don't do any of that stuff :-( so it hurts me when he leaves me for other girls, makes me feel like I'm not good enough. I'm pregnant and working full time & he isn't there for me at all. I'm just hurting rn. I'm trying to be strong but it's hard. I've never seen him act as bad and careless of me as he is right now. & we aren't even talking :-( he doesn't ask how I'm doing & I just don't know what I'm possibly doing wrong, I'm trying to give the baby and myself a life & he just chooses other girls:-/