6MONTHS… WHY AM I NOT OVER IT….?

My daughters father & I were together for 5 years & was doing fine but this past week or 2 I’ve been crying almost everyday… he’s just a fucking DICK!!! It’s not my business which I’m aware of but there’s certain things you just don’t do to someone you onced love out of respect. We both agreed we wouldn’t go back to past people.. we’ll he added a girl back I had so many problems with it just makes me so angry bc there’s one ex of mine he hates and would be crushed if I messed with again… idk it’s 6MONTHS and I’m still in my feelings about it.. I still haven’t slept with anyone because I don’t want too & I already know he has.. I need advice on how to let this go it’s so toxic and I’m over crying over someone that really doesn’t give a shit about me