My rabbit is slipping and can't hop very well, she won't use her back left foot. Why?

She has a lot of bugs (I don't know why) in her hutch and I'm worried that flies or ants might have entered through an opened wound. I picked her up so my dad and I could check for any open wounds, but we didn't find any. I've been really worried about this and she barely moves out of her spot. Do you think she broke her foot or hurt her foot? Do you think we missed any open wounds? Should I be really concerned, or do you think she will be ok? She had babies a week ago and I wonder if that could be a cause. Could you PLEASE answer this? I REALLY love and care for her. PLEASE answer.