Champ,

To answer your question, what activities can you engage in that don't use your brain?

Yeah, that's right; we use it for everything we do. So, maybe make sure you evaluate how you feel after seeing your first client, and be prepared to cancel the others. Do this after every client, just to be sure. If you push yourself to get through them all, and assume you can "deal" with the effects until you get home, the truth is you are damaging your brain that way. There is no "toughing" out a concussion. The symptoms will get worse every time you do this, or extend the length of time needed for recovery.

I know you said you can't afford to go to the ER, but if you had a medical diagnosis of concussion, you would have an excuse to not work for a few days and get some rest. It's something to think about, anyway.