[Peace of Mind]

I'm confused regarding my current diagnosis. I thought I had OCD which was characterized by obsessive thoughts only, however, after having had three major depressive epidsodes in the last ten years, my psychiatrist is talking bipolar. I'll go months even years with no symptoms of OCD, where everythings seems great and then I'll start having irrational, obsessive thoughts which I cannot shake. After about a week or two of these thoughts I'll go into a major depression where I'll get to the point of not wanting to continue on if I have to be haunted by these thoughts. This depression generally lasts about two to three months until the anti-depressents kick in. My obssessive thoughts tend to be things which I know are unlikely and irrational, but I can't shake the feeling of impending doom or feeling that I'll lose my grip on reality. It's like my thoughts are processed as real incidents even though I am aware that they are unreal and irrational. Also, after each episode I feel like I've lost something in quality of life. Although the thoughts simmer down or I acclimate to them, it's like I've been traumatized by them, like someone with Post traumatic stress. Anyone have thoughts on this? Does this sound like potential bipolar. The psychiatrist is talking seroquel?