It's hard to tell if this would be OCD or a BP Mixed Episode. I never experienced OCD, although I have suffered from racing thoughts, very strange fixations, and paranoid thinking during mixed episodes. In your experience, it very well could be mixed based on your description.

Seroquel actually did a lot to help me climb my way out of mixed episodes, and I'm thankful for that. I started sleeping again, and it has a calming effect. The only struggle I'm having with Seroquel now is mood-maintenance, but it's great for many in this area....just my personal experience, and sometimes it's just a matter of determining which dose is appropriate. Tweaks here and there are not uncommon during different phases of BP.

I'm not a doctor, but you might just want to double check to make sure your other meds aren't exacerbating your symptoms. Some meds can actually cause agitation and actually induce mixed mania (for instance SSRIs and certain AD's). You might just want to check in with your pdoc on this just so it can be ruled out, or changed if it is in fact a contributing factor.