Abdominal/Back/Side Pain

The pain had been getting progressively worse up to that point but actually started easing up then. So I thought maybe it was gas after all and dealt with my car issue, but the pain continued to be off and on throughout the day. I did end up leaving the doctor's office a voicemail and they did eventually get back to me. They said it was probably nothing to be concerned about and mentioned round ligament pain. She said drink a lot of water and take it easy. My job is not physically strenuous- I'm a therapist and sit at a desk all day- so I wanted to stay and was feeling OK at the time. But not long after the pain came back worse than ever. I was sweating and a bit nauseous, and it was so bad that there was no way I could focus on work. I didn't feel able to even drive at the time so I took a couple Tylenol and laid down in my office. I nodded off for awhile and felt better when I woke up, but the pain has been off and on since to varying intensity.

When I looked up round ligament pain it sounds like it's a pretty quick thing that doesn't last more than a couple minutes, so I have doubts that that is what I'm dealing with. Right now I feel fine, just drained, but if it gets bad again during the night I will probably go to the ER and if it's bothering me at all tomorrow I will call the doctor again, but I thought I'd reach out here to see if anyone has experienced anything like this, or if anyone experiences round ligament pain that is this severe in nature. I am 20 weeks so while I may have been dehydrated, preterm labor sounds unlikely to me, but then again this is my first child and I have no clue what contractions feel like. 

Thanks-