Cheating

So found out partner cheated back qt beginning of relationship when i was pregnant with first child. We rushed getting together and falling pregnant. He had it in his head i was seeing my ex we were talking alot but i never cheated

We been together 3.5 years now and just had second son

He swore on everyone's lives he never cheated but he finally admitted it after asking relentlessly

I want to have counselling he has agreed but i am massively struggling

He didnt even like the person he cheated with im not tiny but shes a very very big girl etc and no i am not against big people he said it was revenge as thought i was cheating and we were in a bad place he felt unwanted but no reason to cheat which he agreed

Hes said he will do anything etc but im up one minute then crashing down