Pain in lower stomach

tcurnes2005

About two weeks ago I pushed myself a little too hard during my weekly pilates excercise. afterwards, my left side was in pain. since then, i have felt pain in my lower abdominal area while walking, pulling on pants, standing up from a seated position, getting out of bed, and at random times when I'm not moving at all. i have experienced the round ligament pain and this is different then that. any suggestions as to what I should do? 

this is my first pregnancy so maybe this is normal, but I feel like its not. I'm 21 weeks and have been having these pains since 19 weeks.