Your life sounds very stressful and sad OP, and I wish that I had the words to make you feel better. Fantasising about the (presumably) man is not horrible, it doesn't make you a terrible person, it makes you human, but then you have always been human. We are probably the only species that give ourselves such a hard time both mentally and emotionally - and I sometimes think that the nicer, more caring someone is, the harder they judge themselves.
Without knowing a lot more specifics about you, your husband and your family situation, it will be hard for anyone here to offer much specific advice or suggestions, but I am not suggesting that you divulge more to us here.
We don't know if you have any life outside of your home (sorry I can't remember if you said whether you leave the house for work or not). But I feel that you do need to spend a lot more of your time outside of the home, doing things that are particularly for you. Do you have m/any real life friends, do you have interests that are not mainly solitary ones like reading? But then even with reading, if it is one of your pleasures, are there any physical book clubs in your area that you could join? If not, could you start one up now that Covid is hopefully retreating? If attending any sort of gathering is not possible at the moment, there are lots of things, like bookclubs that you can join online - some of them will use skype and other VOIP type ways to get together, and some will just be like MN where we type our communications. But the number of groups that you could join are enormous.
So what are your interests OP? Do you still have ones that you loved when you were younger, or is there anything that has your interest now? Anything from art or photography, to politics, amateur dramatics to cycling clubs? To have at least one interst that mainly takes place outdoors would be particularly beneficial I think. One that I would love if I was well enough, would be wild swimming, but I would join an already established club if at all possible, as there are quite a few inherent dangers involved in it, so having the advice of experienced wild swimmers and swimming with at least one or two other swimmers could kill two birds with one stone. Because I am mainly bedridden, reading and learning a foreign language online are two of my favourite hobbies. If you installed the Duolingo app you can learn a foreign language for free, and maybe you could look for a penpal in the country of the language you are learning. Have you ever just browsed through You tube OP, I have found things by accident that I never thought I would be interested in, and then found that an hour has passed, and it was fascinating!
So spending time away from the house with friends, particularly if you are partaking in shared intetests, would, I think, be very good for you. Also some counselling, just for and about you, might help you think more clearly, and help you realise that you are a lovely person, who has some flaws just like the rest of us, and that that is fine 💐 Good luck OP, and remember that MN is always here, whether you just want to chat, share a problem, or have some advice for others with their problems. 🤗