Cheating fiancé

My fiancé and I have been together 4 years now. We have 2 beautiful kids and we live together. We have started to build our lives together. We are still young (22&23) but I'd say we have had a good healthy relationship until recently. After I had our second child (7 months ago) I think the stress of kids, work, ect got to us. We have been fighting a lot and have said some hurtful things to each other. 2 weeks ago I found out he was texting/calling 2 other woman. No I don't go through his phone I trust him I was using his phone and one of these woman texted and of course after that I was suspicious. I never thought he'd do that.. I felt my heart brake reading the messages. They both were his exes. One of them he talked to mainly about sex. But the other he had asked her for a second chance, told her how much he missed her, and even begged her to come over our place while the kids and I wasn't home... he invited her over on my birthday of all days. She didn't come and didn't seem to interested in him btw. After I found out I stayed with my parents and didn't speak to him for 2 weeks.. he begged and cried for me to take him back. He claimed our relationship was at a bad point and he didn't want those woman .. ect. I missed our place and relationship so I decided to give him another chance. He's been so great since I came home and he even sold his Xbox (his fav thing ever) because it caused many arguments in the past.. I didn't ask him to sell it he just did. He's been so sweet and seemed to miss our kids so much. Problem is Since I've been home I'm finding it really hard actually forgive him. I'm literally obsessing over this situation. I want to know every painful detail of what was said.. i just can't beilieve he sat and texted woman right in my face. I can't believe every time I took our kids to the park or left the house he would call another woman. He was sexting his ex while I was laying in bed with him! How do I forgive this and I feel dumb for talking him back after he did that to me. I keep looking at the messages and the dates and times of the messages to see where the kids and I were during the time. I keep looking at these girls pictures trying to figure out why he's with me when these woman are so beautiful with nice bodies. I let myself go after our 2nd baby maybe that's why he did it. I don't fix myself up often anymore. I'm a mombie 24/7. So this is crushing my self esteem 😞 I also took his virginity maybe he got curios. I'm so hurt and lost any advice is much appreciated. I don't have friends and I'm embarrassed to speak to my family