Kicked a heavy box on accident 35w

I was moving light boxes in the nursery and attempted to slide what I thought was an empty box across the room by kicking it. Quickly found out it was not empty, in fact it was so heavy it didn’t even move.

It was followed by muscle pain in my thigh pelvis and belly. Went to the doctors, had a stress test and they said everything was fine. Baby was textbook.

I feel so incredibly stupid and guilty. Has this happened to anyone before?