Moving on while pregnant

Ex & I are 22 with our first child otw. His side piece is 38 years old. Ex moved out after living together 3 years and already has a key to her house. The same one he was been cheating with for awhile. He said she was stalking him, but that’s a lie. I was blinded by love. The lies don’t work when you’re not in love I see. I’m currently pregnant with my first child and we wasn’t together when we found out. Separated and I was already 1 month pregnant. We remained close until 6 weeks ago. We stopped communicating unless it’s a doctors appointment. I declined sex since I know he has been with her. Problem is he hasn’t admitted to anything, but I have proof. I tell him the dates of appointments and we go together. He showed up drunk on my doorstep at 12am & attempted to return 3 nights in a row last week. I also told him no last night. We don’t text or anything. Why is he showing up to my house? He has someone that’s obsessed with him. He can’t have both. Well I’m not accepting just anything so I completely left him alone !