I don't know what to do!

So a few moths ago, I found out my husband had an IG and was talking to a friend from school. I messaged her and she said she didn't want any problems. We left it there. Come to find out two months later, he made another account just to talk to her, my heart broke reading all the things they would talk about, I posted everything on FB and IG, everyone that knows her knows me too. She has 4 kids and is married, her youngest is 2 years old. I have two kids with my husband, the youngest is 6. It still hearts me so much till this day but we are still together and he acts like nothing ever happened. Well I've been having morning sickness, I did just get over a cold so it might have to do with that. I have an IUD and don't believe I'm pregnant. This morning he told me "you better not be pregnant, you can't be pregnant" I was like WTF! I told him I wasn't plus I haven't missed my period, he flipped out, a side of him I've never seen before. I don't know what to do, I ask him why he's with me if he's not happy to just leave, but he just leaves and won't talk about it, I don't know what to do. I know what I should do but I'm scared of how to deal with it. Someone please help or give me advise, we've been together 11 years and have two kids, I don't want to break up my family but I don't want to live this way 😔