Cheated on

I found out about 2 weeks ago that my husband has been cheating on me, i confronted him, told him to leave and everything but he doesnt want to he says hes willing to do everything to fix it... I decided to stay for my baby and because i somehow still love him and its really hard for me to just let go. But lately i just remember everything i saw and i get angry and depressed since i just had my baby 4 m ago and i feel fat n ugly. I don't know how to deal... Has anyone gone through this and decided to stay ? Does it get better? Or its just a waste of time ?