I can relate somewhat. I'm 5 months pregnant. I have a 1.5 year old and a 4.5 year old at home - stay at home mom. I really want this pregnancy to be over because it's the most frustrating pregnancy. I got bigger alot earlier and already feel/look like I'm 8 months pregnant! I'm normally very active with the kids but it's so hard just to get on the floor and play with them, let alone run around outside with them.
Luckily, I have an understanding husband. Or rather, he doesn't get much choice. I just tell him that I'm going out 2 evenings a week. I don't ask him. I tell him I need a break and he would too if he was around the kids 24/7. I put it on the calendar, tell him what night it is so he knows to be home and then I leave. It's very healthy for kids to get a break from mom and have time alone with daddy. As far as I'm concerned, the kids are his responsibility just as much as mine. He gets a couple night out each week and so do I.
I play ice hockey and still go to practice one night a week. I'm too big for my hockey gear, but I put the skates on and help teach some of the newer players basic skills and run the practice when the coach can't make it. The other night out is also 'me' time. I'm in a couple local mothers groups so there's at least one mom's only evening event a week I can go to. I >need< these nights out. If I don't, I start to go nuts, get very short tempered with the kids and could see myself getting depressed very easily. I also take the kids to several playgroups and field trip events each week through the mothers' clubs because even though I'm with the kids, I still get to talk with other adults about grown-up stuff.