Wow! You took the words right out of my mouth on this one. I also have OCD and experience the same kinds of hyper nervousness.

The only things that I have been able to do to reign in my brain, heart rate, etc are:

1) Stop and take a brisk walk. Sometimes expending some adrenaline can help me focus more. If I happen upon someone to talk to about something completely unrelated to my stress it will allow me to step out of the panic and reorganize my brain.

2) Write a to do list which is organized with the most critical tasks first. If I can start working on some items in a logical order then I can start to relax a little when I see even a tiny bit of progress.

3) If the to do list starts to stress me out, I will try to distract myself and complete one little task. I'll start with the task I want to do the most.

4) Make an emergency appointment to see your psychologist or talk with a trusted friend. Just talking about your stressers and getting some sort of 3rd party feedback may help to calm you down.