What should I do about this?

My wife is pregnant she's cheating on me with one of my bandmates she won't leave him alone it's really upsetting me. I love her more than anything yes the baby is mine they haven't even been together that long I'm hoping it's a silly crush hoping it'll pass but I can't stand it she even posted a picture of her kissing him. She even posted that she's in a relationship with him. I'm sick of it I been with her for 2 years after trying 3 times to get pregnant she finally did now she goes and cheats on me without telling me. I'm so mad and upset over it I'm not comfortable with leaving her though. What should I do about this?
What should I do about this?
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