Missflip, I am sorry that you are feeling down again. I know what you mean about not wanting company but then feeling bad because you don't want company. Your husband is right though. if you don't feel up to it, then you need to take care of yourself first. I think they will be more understanding than you think. (speaking to myself also). Sometimes I don't even feel like calling my mother and then I feel guilty that I didn't call and when I do call I apologize and she says it's okay because she knows how I get and because she knows that I love her no matter what my mood is. So don't beat yourself up about it.
Sometimes, I will do my best to make myself get up and out of the house just because sometimes it does make me feel better. So maybe one of these times, you will be able to without much effort and then before you know it, you won't even be thinking about it. and remember we are here for you.
PS. When I was pregnant last time it seemed to just go by so slowly. At the time I didn't know that I am bipolar, but I experienced a lot of the same things you are now. I tried to keep myself busy as much as I was able and that helped. just keep thinking, you are almost half way and then before you know it, you will be more than half way and so on. at least that worked for me, most of the time.