I would call your doctor. i think it's pretty normal for the baby to become less activie b/c of the tight living space but I would call to make sure. The back pain could be a couple of things...maybe back labor or just aches from carrying around extra weight. I would call just to be sure. That is why your doctor is there...don't feel like you are annoying them. It is better safe than sorry. Good luck mama!
Back pain is pretty normal in your last trimester and really shouldn't have any affect on your child. You on the other hand...that's different...we've all been there - it hurts, but it will be worth it in the end.
wow that small? mine is measuring at about 5lbs & i'm 32 weeks along i would talk to your ob about the slowed movement, my baby has slowed down alot too, but idk if it's b/c he's getting cramped in there or not & i plan on calling my nurse in the morning GL