You so need to listen to your body because if it doesn't bother you or baby you should be fine. I asked my dr. early on in my pregnancy if there was anything i shouldn't do & he said ever women's different & there is no one better to determine what what you should or shouldn't do then you. I was so worried because I have found that my baby & I both like better when I lay on my right side then on my left like most women. My baby moves better & I am more comfortable & so I asked if that's OK & dr. said for me to listen to baby & body. So I say to you the same words listen to your baby & body.
I agree with the pp. I am 38 weeks and still bending over to scrub my tub and lifting kiddos at work. If i feel short of breath or a twinge of pain, I stop what I'm doing and rest.
I would say listen to your body....its not bad to help your son and lift some if you have too...I've know a lot of moms that continue life like normal even though there pregnant... Just listen to your body and it should tell you if your over doing it...hope that helps