Recently stopped being friends with my ex.

We stayed really good friends after we broke up, but last night we had a fight because my ex lied to me for a month and wouldn't give me a straight answer about getting back together only to find that they have been dating someone else that whole time.This is after I cleaned their super messy apartment during their depression, went to the ER with them in the middle of the night and looked after their dog for days.I was the one that said that I didn't want to talk to them anymore and it didn't seem to bother them.But I miss my ex and I can't help but wonder if I've made a mistake.