I love my husband but..?

I happened to fall in love with a colleague at work.. We've been working together alot recently and I just can't get him out of my head. It started with admiration but now it's turning into much much more. I am married to an amazing guy and have an amazing kid and my co-worker is also married with kids. But for some reason, he's no longer just a friend to me. I've been been trying to stop myself from communicating with him (except something imp about work)... But I feel like I am dying from inside.. don't know what to do, never told anyone about my feelings but I can feel that my co-worker has some feelings towards me too.. I want to keep working with him cuz I enjoy it.. But I don't want to feel as if he is threatening my mairrage! What can I do?