17w3days

Lindsay
I'm 17w3d and I have tremendous pressure on my groin area, when I lay on my back it hurts, if I lay on my left side it hurts, any ideas on what it could be? Doctor said my placenta was low, but didn't go into details on what that means, and also got checked for a bladder infection, and that was negative. Any help is appreciated :) thank you in advance :)