I have the same sharp pain on the lefthand side too. I just had an ultrasound done and there was a 2.5cm functional cyst there. That explains the sharp pain, the pressure on my bowel and bladder, the heavy feeling between the legs,and not being able to sit down for more than a few minutes without it hurting. Apparantly these cysts clear up by themselves after 2-3 months. I'm giving mine one more month. If I get those symptoms again this time round then I'm afraid it's just not worth keeping the Mirena.