PE, Chest Pain and Lightheadedness

Hello.  I am having symptoms of very bad lightheadedness (I can feel this even when laying down) and chest pain(increases with light exertion).  The chest pain is sharp, stabbing at times.  It does also burn in the lung area where I can pinpoint the pain. I also have pain in my left arm and underarm area.
These symptoms have been going on since Nov 2010, and have in the last 2 weeks gotten worse.  I have had a stress test with echo,standard chest CT with contrast, echo of heart and several basic blood tests.  My lightheadedness is getting worse along with my chest pain.  I also had a D-dimer test recently(2 weeks ago), which was negative.  My thought is the possibility of me having a clot in the left arm that has gone into the chest and has caused me to have bad chest pain and worsening lightheadedness. So bad that I am not sleeping well.  The lightheadedness also causes me to wake up many times. Would the D-dimer test pick up a clot that may have been there in the arm since November of last year?  I am concerned that since I did not have a CTA, that a PE could have been missed, with just having a standard CT with contrast. I have this concern because of my job for the past year, requires sitting down for long periods of time doing documentation work. Wonder if a clot may have traveled from the leg, to the left arm/underarm and then to the chest.This has been going on for too long now, and has gotten worse. Don’t think I would be as worried, if I didn’t have the bad lightheadedness that has gotten worse.  Hoping to get better since I have two young kids.  Thanks so much for your time