Having an affair with a married man. What should I do now?

I have been married for 15 years to a good man. He is good with the kids, makes a good living, loves me uncondionally, and I know he would always be there for me. Yes I love him but I feel like I missed out. We were married young and I never had the chance to experience other men. Not to long ago I met a married man and we just seemed to click. We have been having an affair for awhile now and it has been great!! I find myself wishing he would leave his wife to be with me but I know that will never happen and now I don't know what to do. Keep seeing him on the side and let it run its course or stop now? I know it would break my husbands heart if he finds out and I do feel guilty but it feels so good! I am so confused and I really don't know what I want to do.