Okay - people say not to snoop for a very valid reason - it's too difficult to act as if and turn the R around if you are steamed up about the fantasy email they sent to oW yesterday. So a lot of people would say, put your energies into making your R with h exciting and new and fun, and even if he iS having an A now, it will fade away as your marriage becomes a more interesting place to be.
That being said - if your position is truly that you no longer want him if he is currently having an affair - and you are CLEAR on that in your own mind - then I think it's reasonable to try to find out the truth.
Ways to go about this? some people have downloaded keystroke logger programs onto their computer so they can see what H has typed.
You might enlist a friend to spy on H when you think he might be having an opportunity to stray. (or a local fellow DBer?)
Check cell phone records. (I know some people on the board have managed to do this even when their spouse hid the bills, most companies have a feature where you can check it online, not sure how to go about doing this, but someone here probably knows.)
What time does your H have available? I would have thought my H didn't have any opportunity - I found out about his affair by accident from the computer. If I HAD had suspicions, I would only have been able to catch him at lunchtime from his work.