I started taking zoloft about 2 years ago. I had to change to zol...

I started taking zoloft about 2 years ago. I had to change to zoloft from paxil because it stopped working. I was put on it for being irritable and having major mood swings and anxiety. While on zoloft I have had terrible thoughts about things that could go wrong. I turned into some sort of hypocondriac. I also would get horrible headaches and convinced myself that I had brain cancer. I also had little motivation to do anything. I couldn't last at a job for more than a couple months because I had no motivation to go to work. When i first started taking it I had a hard time falling asleep. After a couple of months my sleeping patterns became normal, and my headaches went away. Recently I started taking birth control and my old symptoms flaired up again. I now can not sleep at night. I stay awake all night and sleep all day, and have a continuous headache. Has anyone else had these problems or side effects?