So hurt, Marriage over so fast. WTH

I caught my husband cheating 3 weeks ago. It has been going on for 4 months. I am 8 months pregnant and we have a 5 year old son. I found out the day he was supposed to take a trip out of town and he still went! I left the house and was not there when he came home on Sunday! I went to stay with my mom.

He tells me he wants to work on things he just needs time to get things ready for us. He stops at my moms house, pulls out all the stops to make me feel so loved and I give in and have sex with him.

The next day he is a complete ass! We don't talk for a few days and then he starts sending me pictures of his junk.

I find out from a friend he is still seeing the OW. I get in my car and drive to my house at 1 am...unlock the door and there they are! IN MY HOUSE!!!!

He was lying the whole time. I go today to get my things....she has moved in her stuff. They were having sex in our bed.

How can someone do these things. WE are STILL married!

I am so sick and heartbroken.