Round ligament pain

Can anyone explain to me what round ligament pain feels like? I feel like I have a stretching feeling in my uterus and on my sides. Yesterday it was so bad I had to take tylenol and called my doctor. The nurse told me that it most likely has nothing to do with the baby (in a harmful way) but most likely the stretching of the uterus being that we saw our baby Tuesday with a healthy heartbeat of 167 and growing right on track. This is my rainbow baby and pains like this make me nervous something is wrong. I am currently 11 weeks and 3 days today.