It sounds like you and your fiancee need a break from each other or have a long chat to work things out quickly. Although it's normal to feel low and depressed about yourself because of the constant pressure he is putting on you, you should know and emphasize the fact to yourself (and him) that it is not your fault. Not at all. Don't think for one minute that it is your fault that you cannot meet his demands, so don't feel bad about yourself.
If there is nothing that can be done about the situation, perhaps there is another place that you could stay, perhaps a visit to your mother's or a sister's where you could be helped a little more than not, and can be relieve of your duties so that you can recover, and until the sickness subsides. The stress that your fiancee is causing you is not healthy emotionally or physically, and could be making your symptoms worse.
He needs to realize that it is his baby too, and part of what partners do is support each other. The baby is his responsibility just as much as it is yours. He doesn't just get off scott free.......what you have to deal with is nothing in comparison to coming home to a little bit of laundry on the floor and a few dirty dishes. You have to deal with looking at the dirty dishes and laundry just as much as he does.
He should be supportive and help you out because part of the baby-making process also belongs to him. And it doesn't end here either. Does he think that once the baby is born, things are going to be better? A child brings so much more to the table...sleepless nights, toys strewn on the floor, much more laundry... If he can't handle it now, how is he going to be mature enough to be a good an supportive father and partner when the time comes?
I understand that he is a hard working person and needs that space of comfort that is what he calls home. Just think of it as yourself as the person who is working all day, and never gets out to go to a place of comfort, and on top of it, there is someone who blames you for not keeping up when you are really doing the best you can.