Am i overreacting?

I was 7 months pregnant when i stumbled across a txt that another woman sent my husband (that day i had run out of crdts and so thought to use my husbands phone to make an urgent call). It seemed like it had been going on for a while...theyd even discussed me, my husband telling her how i dont give him a blowjob and do not satisfy him in bed. Nd she inviting him over after work for sex. There were messages where he was asking her to take her bra off and all sorts. That day just broke me. We have only been married 8 months and i loved and trusted him more than anything in this world. 2 months down the line i am still living with him just because i love him but i can never trust him again. Whenever the topic comes up his excuse is that he never slept with her and its not cheating and was having some fun thats all. He says if he wanted to he wudve put a lock on his phone but he never did cos according to him he has not done anything wrong. I hate myself for loving him so much cos i feel dead from inside. How could he do that to me? Nd dat too wen im pregnant with his baby. Am i overreacting? Would u not call that cheating??

** id like to add he did apologise to me after i confronted him and said he made a mistake. But he has lost my trust. To me cheating can not be a mistake, he made a conscious choice. Every single time he tells me he loves me now i feel as if im being torn from inside.

I wish i hadnt read his txts, i am due in 5 weeks and i cannot cope with this stress tearing me from inside anymore.