I know what you mean for the past 2 years almost every waking moment at least in the back of my mind (if not in the front) I was thinking about PCS.
Is what I am doing now going to have consequences? What the heck is wrong with me? I sure hope this isn't really, super serious! What can I do?!?!? Everything causes pain but I can't just lie in bed!
For me I still can't remember the 10 hours surrounding the accident and I have only vague memories of that entire year, so I also have a lot of questions about what happened. People don't understand my desired to fill in the blanks, so only slowly have they been revealing details, but this makes me even less able to stop thinking about it.

All I can suggest is maybe write it down, or find one person who is willing to listen all day long for a year about your worries and highs and lows. Some way of getting it out because inside it will just fester.

But, to answer your question yes worry does make things worse, but bottling it up or drugging up does not seem to treat the start of the problem.
I think don't stress about it just let it out somehow.

First make certain that you aren't going to die...ie, get an MRI and MRA of your head and neck to make sure you aren't bleeding or have bubbles floating around, then start finding little things you can do and slowly work up your ability to do them for longer or finding new things to do.
Lastly DO NOT HIT YOUR HEAD AGAIN!!!! Do Not Even Shake It!!!

Good Luck!
Margarite