Emotional mess

So today I finally had the guts to confront my SO about sleeping with his ex and left. When I got pregnant in August they slept together and I contacted her after I got a positive STI result to inform her to get tested. She said she had told him she had something but he failed to tell me. Fast forward to last week. His ex was in town and he was acting shady, not answering texts and going out all night well that created a fight that lead me to go to my lawyer pertaining to custody and child support once the baby was born. Then last night his ex messaged me and tells me they were hanging out. I text him the following morning to see if he would lie and he did until I mentioned she already talked to me. Now I’m just crying all night because I don’t understand how anyone could put the mother of their child through that especially knowing I had a similar situation with my oldest child’s father cheating the whole time I was pregnant and the toll that was put on me. I honestly don’t know how to wake up and just go on without bursting into tears because it hurts so bad. I’m sorry, I just had to vent because I can’t really vent to anyone else without feeling embarrassed 😞