Gross fiancé?

I’ve been with my fiancé for over 3 years now, I love him but he is once of the grossest people I’ve ever met. I know I should’ve seen the signs more at the beginning, but I didn’t. I got with him when I was 19 and he was 30. I just got my own apartment months before we got together, and I’d visit his apartment but I never fully paid attention to little details around his apartment or how gross it really was. Close to 2 years into the relationship I moved into his apartment and that’s when I started noticing more stuff that I somehow didn’t before. The bathroom and kitchen were the worst areas. Dry pee all over the toilet, running down it, and all over the floor, when he’d get done peeing sometimes there would be a wet spot on the outside of his pants from it. One day I started to go down on him and it smelt like it was rotting and I told him I couldn’t do it. I figured out it was because with the pee, he’d also cum and not even wipe it off at all, and work out and basically wear those all day. I told him I would never do anything with him again until he cleaned himself. Poop streaks on every towel he’d use. The shower was never cleaned (till I got there). Same for the floors and cabinets. The fridge had sauce and crumbs everywhere inside. The dishwasher had sooo much old rotting food in the bottom of it. Everything was just really gross. I honestly just assumed he didn’t care because he was living alone for awhile and I thought if I cleaned everything it’d stay pretty clean. It didn’t, but I thought at some point it’d get better if I kept asking if he could clean up after himself. Pretty quickly though I started noticing how bad his neighbors were. One day I was walking down the stairs and one flicked a cigarette on me, they’d leave trash everywhere outside and cockroaches started coming out of the wall from their apartment. I’ve never had to deal with cockroaches so that made me panic and we were trying to treat for them and it wasn’t getting better because of the neighbors, so we started looking into buying a house together. We found a house pretty quickly and moved in about 2.5 years into the relationship, he proposed the night we were moving in. I decided I wanted a separate bedroom and bathroom, thinking that’d help. But it really didn’t, and any time I ask him if he can clean up the messes he makes he pouts and says I’m nagging, even if i only ask once. No matter what I do I can’t keep the house clean(we both work 40hr weeks). At some point he started coming into the same room as me, even if I’m eating, he’ll just fart, it sounds and smells like he literally poops. I started repeatedly asking him to stop coming into the same room to do and he just kept saying that I don’t love him (pretty sure as a joke) but he won’t stop and I’ve asked so many times. He doesn’t wash his hands after pooping or taking out trash and will literally eat and do multiple things after. I have literally spent all day cleaning before and woke up with hot sauce and crumbs everywhere and when I ask him to clean it he’ll sweep the crumbs onto the floor. One day I came home from work and saw a wet spot on the back of his pants, I asked about it and he said he didn’t know what it was so I for some reason smelled it and it was clearly cum and he said he did stuff hours before. He sat in his own cum for hours before I got home? I was so grossed out. We haven’t done anything sexual at all for months, I feel bad, but I just can’t bring myself to wanna do anything. I haven’t told him why. I wanna fix everything because I do love him, he’s usually a great guy other than how dirty he is. At this point I have no clue what to do. I can’t talk to him about these issues, he’ll immediately think I’m nagging no matter how I approach the conversation. I’ve mentioned couple therapy and he thinks the idea is stupid and that he didn’t think we had any issues. Has anyone else ever experienced anything similar? I’m slowly losing patience, I really don’t want to leave, but I literally have no clue what else to try.