Whats his problem, why hasn't he called me?? Help!!?

My ex left me with 2 kids and now I'm 36 wks pregnant now. He has not been there for me this whole pregnancy. I even found out that he was talking/sexing another woman. She knows I'm pregnant and can careless. He told me he met her 7 months ago. Well recently he told me he wanted to spend the night. I let him. I made him feel really comfortable. I didn't even bring up things I wanted to talk about because I didn't wanna make make him feel uncomfortable.(like how come he hasn't bought nothing for my baby or questions about that girl I know he was/is messing with while I'm pregnant.) So we had a good night. We had good sex something that we haven't done in like 4 months. Now its been 4 days since I dropped him off and I haven't even heard from him. He didn't even answer a text I sent him. I refuse to call or text him more then once. What's his problem?? Advice plz and how should I react when I finally do hear from him??