Oh, I totally identify and empathize with your situation. I was married for over 20 years to a man to whom I could not relate emotionally. In my early thirties, I began taking an art class at a local college, and became totally smitten with the professor, who elicited from me all the inspiration and emotions my marriage lacked. It ended because I could not become involved with him sexually...I just couldn't, even though he said he'd "take care of me." I did tell my husband shortly thereafter, and he just dismissed it, though he was hurt in his own shallow way. This took me ten years to get over.
Divorced 9 years now, I have never regretted leaving my husband, though it was not for another man, instead waiting till my daughter left for college.
You're in a real pickle here. If this man with whom you're having the affair says he loves and will never leave his wife...you need to extricate yourself from him, painful as that will be. Also, if your marriage is so unfulfilling, address that problem sans boyfriend.
LOve
Patty