Help maybe

Idk if anyone can help me, when I can't even help myself lol. Here's the situation..I've been with my bf for 3 years. He was the perfect man, he treats me like a queen, he spoils me, and makes me so happy..I think? I'm 35 weeks pregnant with our son, but he has one habit. He constantly cheats on me, I dont mean physically, I mean online. Sexually texting other women, dating sites etc. I have caught and called him out many, many times. Its non stop. At this point, I look over and see him deleting multiple conversations with different women, and I know why, but I just become numb to it, I guess. I still love him so much, and hope maybe something I change, something I say, maybe will make him change into the person he was when I felt he loved me too. I dont know why I cant just leave him, can someone maybe give me some insight on what could be wrong with me?