I am cheating on my husband!!!

I have been with my husband for 6 yrs we have a 4 month old baby I dont know what i feel for him anymore i feel like the last of it went away when he relapsed on drugs and messaged my sister talking about wanting to fuck her ! I'm a SAHM dont have family near me all is about 3 hours away. I dont know what to do I dont want to break our family apart I know my daughter loves him. Honestly speaking I'm scared financially because I dont work and I know I wont be able to spoil her as he does.. I know if I leave he will return to using drugs and lose it all again I dont want that. I am struggling between leaving to live with my sister 3 hrs away (she offered to help) or suck it up and try and make this work for our daughter. Is him doing what he did enough to file for a divorce ? Or am I exaggerating? I know I have to end my affair i know it's so wrong I drown in guilt every day!

-the affair started after he messaged my sister (not an excuse) .

- I am not with him for the money he just started this welding job about a year ago with my help. A couple weeks before he got the job he was living on the train tracks homeless skinny as hell from the meth I went there myself and brought him home stayed with him thru the withdrawal. I was the one supporting us for the 5 yrs prior to him getting this job.

-when I met him I was 19 in college and working... he was a drug dealer (didn't know) I have stuck by this man as he was homeless, jobless, drug addict, in jail/prison, and I stayed faithful to him throughout it all in hopes he would change. He has taken all of me I have given him everything I had.