Finace recovering from chemotherapy ...any right to be upset?

My fiance and I have been together 8 years, last three of which have been spent with him in or recovering from chemotherapy treatments. I have been supportive and put my needs on the back-burner for the most part. Our life obviously has not been great these last three years, even though we're in our late 20's, due to the effects of his chemotherapy on his drive. I found out yesterday he has been to online . I am hurt and saddened by his confession. If we had a fullfilling life I would not mind him satisfying himself....but I am the one left frequently unsatisfied. (Don't get me wrong, when we do have it is great, we just don't do it very often.) I am ready willing and able to have almost anytime, anywhere. I feel like I've put my needs on hold these last few years and now that's he's back and able to get back in the game, I find out he's turning his ual desires (which I thought were not here) to . Am I irrational to feel hurt by this?