A couple of things. I went through this and cheated, dh does not know but the loss of the other relationship caused me to spin from manic (and hypersexual) to a severe mixed state mostly depressed that landed me in the hospital for the first time. It took quite a while to recover. So know that it can cause a toll on you as well as your marriage.
That being said, what are you doing to alleviate the (hypo) manic state that is most likely to blame for your hypersexuality? An honest visit with your pdoc is probably in order. Remember hypersexuality is on the symptom list for mania so it wont be a surprise for him or her to hear it from you.
Hope this helps some, I really do understand how hard this is.