I would also think a blood clot, that have a test they can run called a D-dimmer to test for blood clots, and i would also recommend that your monitor your blood pressure when changing positions (orthostatic Blood pressures) because if there is a sudden drop in your BP then your physician will need to follow up on that. To help with the dizziness when changing positions you should make sure that you take your time, take some deep breaths and rise slowly.
have they tested you for a blood clot? it could be that I would ask about this dont give up you have pain something has to be wrong