I feel like a disease

26 years I’ve been the good son, the good friend, the good partner. Now I barely speak to my parents, I only just rekindled my friendship from childhood, and I’ve cheated on my fiancée. I haven’t felt anything for over a year, any emotion except for fear and discomfort. I was able to think when I stopped talking to my parents but now they think I hate them. I am glad I rekindled my friendship but I’ve lost so much time with him and his family, his daughter doesn’t even remember me. I thought because I was numb and this woman made me feel something for a little that intimacy wasn’t a problem, I can’t even say I wanted to do it. Now I can’t tell my fiancée because I’m the only person who has ever cared she has said. I’m the only one who’s never forced myself on her, I’ve never yelled at her or raised a hand. I’ve done the bare minimum, except I failed simply being a loyal partner. I have a daughter, and I couldn’t imagine what’s I’d do if someone did this to her and I’m not sure what is wrong with me, I’m not sure why I’m like this and I’m growing so very tired of being me. I don’t want to be anymore. I take everything good I have and I just take advantage of it, I’m not sure why but I would like some other answer than I’m just a bad human.