What do I do?

I think my man is talking to his ex girlfriend again and hanging out with her and I don't know what to do. I texted him we need to talk but then panicked so I just told him we need to talk in person. I don't know what to do. Like I don't want to just flat up ask him if he's seeing her again, i'll just seem crazy. But whenever I think about them together it makes me feel sick, numb, like I can't move or breathe. I just don't know what to do.