Carrying heavy stuff. Please doht judge

I know you aint supposed to carry heavy stuff while pregnant. But i live alone with my 2½ year old who weighs 16 kgs. I try not to carry him a lot but if he sleeps off, i carry him to bed. I have heard that if you are useŕd to carrying that weight from the beginning of the pregnancy, then it aint as dangerous as sudden lifting of heavy weights.

Anyway. So am 20 weeks pregnant. I keep everything my son doesnt need anymore in the basement. Also have clothes he is yet to grow into there. So he outgrew a size and i had to go pick out new clothes and store the old for next baby. While there, i had to rearrange the whole basement storage system. Wanted to bring the new born clothes my son used 2 years ago in a more accessible place as i will need them in 3 months to set up for baby. I had them at the back all this while because i didnt need them. So i moved christmas deco and clothes he is outgrowing now further back. Roughly it was 20 boxes weighing between 10 and 25 kgs. I wasnt carrying them far. Just the whole back and forth.

I needed to do this before my bump gets even bigger and reach third trimester. Also i couldnt ask my mom to help me, because she has back problems and is away in rehabilitation. My husband wont come back until baby is here and that is a little too late to sort everything. I might also have a second csection which would mean doing this later is a no go. I have 2 other friends, one doesnt think i should prepare, the other has 2 babies below 2, and my best friend doesnt want to talk to me because she had 2 losses and cant handle being around me pregnant. So it is up to me to do these things

After i was done, my back hurt and my feet too. Now am wondering if i hurt baby or am just physically tired. I didnt fall or hit anything on my tummy. Just need some reassurance that everthing is ok. Also why shouldnt we carry heavy stuff? I actually have never understood the reason. What should i look out for. Am hoping to sleep and wake up feeling better. Thanks for the advice in advance.