Hi. I can recall a time of plotting to cheat on my husband and wishing we were separated so I could. I chain smoke a lot too. The desire to cheat always came during hypomania for me as hypomania = hypersexuality. I don't drink or gamble, but I drink coffee like it's going out of style and smoke like a chimney. During my hypomanic phase, I did engage in online affairs via internet sex, and my husband found out. We even split up for a few months over it, so I can relate to some of what you have been enduring. I can't diagnose it, but I can surely empathize. For sure, seeing a therapist is a great idea. All the best to you.