Hello OP
congrats on your pregnancy! what a blessing.
its a really crap situation your in, everyone saying to leave, is right but its totally down to you. it may not be the decision you want to go down and that's a decision you will need to live with and others will need to respect.
I found out my partner cheated on me last May, he was on an online dating app and messaged a girl saying he was single etc etc and its was actually my FRIEND! he didn't know we were friends and she called me straight away to tell me.
I was devastated and cried beyond belief, we had only just got engaged and we have been together 8 years and not long bought a house together.
I am now pregnant with his baby and we are in a good place.
I chose not to leave him. he told me it was just the once, and I gave him the benefit of the doubt as I had no proof of any other instances. and when I weighed up my life, financially and mentally, I took a view on it and decided to stay. obviously if it ever happens again then 100% were finished.
but you have to do whats best for you, only you are in your shoes and walk your path. There will need to be changes in your relationship if you stay with him, and this will have to come from him.
I confided in my mum for support and didn't tell anyone else due to embarrassment. Do you have anyone you can confide in? it definitely helped me as I didn't even want to be near him at that point and felt so alone and ugly.
I know its really hard to deal with, especially pregnant but you will get through it, with or without him.
im sending you lots of love- hope you are ok xx