Exercising :(

Last night I was at the gym and I think I may have over did it!  I was on the treadmill for 45 mins walking at a brisk pace with a high incline.  I felt fine afterwards until I got home.   I have been running and workout throughout the whole pregnancy, so Im surprise that I am having pain.  The pain is around my round ligament area on my left side and back.  I had a rough night sleeping bc of all the throbbing.  When I apply pressure to the area its a little tender.  Should I be worried.  Baby is still very active too!  Im planning on taking it easy today.  Has anyone else felt anything like this before???