Ex moving on but still saying he loves me

So I ended my relationship with my ex because he was selfish and never put myself and our daughter first. I left when I was about 10 weeks pregnant with our second. Now I get that he’s aloud to move on since I ended things, so I asked the question today that I didn’t really want to know the answer to but I did. I asked if he had been with anyone since we spilt up ( 5months ). He told me that he had. He has been saying how I’m the love of his life and that he doesn’t want to be with anyone else. Im currently 32 weeks pregnant and I’m an absolute mess as I just can’t understand how you can be so “madly in love” with someone but go and sleep with someone else...