picking up heavy things

So, what is the deal with not picking up heavy things? I am 7 weeks and everyone is saying don't pick up that or don't pick up this. Can I hurt the baby by picking up heavy things? Can I lose the baby by picking up heavy things? I work at a company where I fill and carry propane bottles on occasion, some weighing up to 60lbs. I can call someone to do it but that takes so long and I feel like such a wimp. but I just filled one and carried it to the car (40lbs) and now I am worried to death that I have messed up big time.

it can cause you to misscarry! So stop picking up things 

Straining yourself, and/or picking up heavy things put a strain on the placenta, and can stop functioning correctly.

If your body was used to it before, you should be ok if you are not uncomfortable doing it. If it were me, I would stay away from 60 lb tanks just to be on the safe side.


Edit to add:
I was lifting weights before I got pregnant. My doctor told me I could continue lifting what I was already used to, but not to add anymore weight.