What should I do?

Okay so please don't judge me, but after I broke up with my boyfriend in March. It was mutually ended, but there was a lot of hurt so I started sleeping around. I slept with at least 20 guys. Well the last guy I slept with for a little while we texted and had sex a couple times well just recently I found out he's had a girlfriend for years. So the whole time we were sleeping together he was in a relarionship. Well the girl is friends with my best friend and I've only met her once so I'm not sure if I should tell her or not. He also always told me he never wants to be in a relationship because he enjoys sleeping around too much. Another problem around the time I stopped sleeping with him I met my now boyfriend well either my boyfriend or the guy with a girlfriend is the baby's dad. Should I tell him that he possibly is even though he doesn't want children and made it xlear.