Am I being stupid (yes)

The other day my boyfriends baby’s mother dm me on Instagram and said he was cheating on me with her, so I asked for proof and proof is what I got!!!! I’m not sure what to do at this point because he was telling her he loves her and only wants to be with her and their baby, but he said he was confused and just knew he needed to do the right thing for his daughter. I know that doesn’t excuse the fact that he cheated but I just don’t know what to do ☹️ someone pls help 🆘🆘🆘🆘