i Dislike my mother in law so much

I used to love this lady so much and now i  Cant stand her... Why because when my husband and i seperated she became besties with the side chick. The most hurting part  he left two days before christmas and she left christmas day to ny to spend it with him and her a lady that was 50 yrs old my husband was 26. He was with her for $$. That was about 2 yrs ago and i cant get fucking ovet it... I cant trust my husband last time i kicked him out was a yr ago for calling her again... Now im pregnant and i wanna trust him not cause i want to but because i need to for my sanity ... I need to bury this... Because i love my family and i feel stuck