My relationship ended, and im back to smoking

Hey guys, i have been in a relationship for 7 years. Most stable and happy i ever was. 3 days ago she decided to break-up with me because she didn't feel excited about me anymore, and wanted to see other people. This situation brought me back to my smoking habits.
I lost a lot by the relationship ending. I moved away from everyone i cared to be with her. I sacrificed so much and achieved so much professionally, and now i don't see any other option than to leave this place behind and move, and lose everything. I didn't really had any friends here, only friends of her who i hang out. Now i feel like shit, depressed and at my all time bottom. a month ago we were planning to have kids and get married, and now i'm left alone stranded with nothing to hold me.
Smoking now is the only thing that gets me through and i don't know if i'll be able to stop it now. Any advice?