Don't know how I feel

C 💕✨
When I was 17 weeks preg me & my fiance split, it was a really hard time but then about a month ago we got back together. He admitted to kissing another girl twice while we were split, things didnt add up and I didnt believe things he said. At the weekend the girl added me online and told me everything including screenshots of messages between the 2 of them. He was basically living at her house for a month, had sex plenty times, he even told her he loved her. I confronted him told him i knew everything and showed him all the messages. He apologised and promised nothing ever went on when we were together which the girl has confirmed (we are on ok terms and i am so glad she told me the truth) its the lying which has got to me so much and the extent he went to to cover up everything is terrifying. I really want things to work out with him since our baby is due in 10 weeks. I know everyone makes mistakes but i just dont know how to feel. I dont know if i'm looking for advice or just need to tell someone. He has promised he will never ever lie to me about anything again as he realises the truth will come out, i have told him if he lies about any tiny thing ever i will walk away from him and never look back. He said he will do anything to keep me and that he never loved her he just missed me and never thought we could make it work and his head was a mess. He has stayed over at mine the past 3 nights i told him i dont know if and when i will be ready to have sex with him again as i cant get the thought of the other girl out of my mind 😖 i just dont know how i feel and if anyone has been in a similar situation can you share your experience or advice please xx