Hi Christine,
I know that working out can sometimes be a bit addictive andn you seem to want to be in tip-top shape etc. but if the sort of workout that you do even slightly has such a bad effect on your brain, I would really listen to what that is telling you: You need to stop doing it, at least for a while.

It is really important to let your brain recover. That is the most important part of your health right now, rather than what you are working on in your workouts.

Your last concussion was this month!!! You don't need to be working out yet.

When you do start again, I found that high impact workouts did not feel good, so anything that involves jerky movements, e.g. like bastetball, even running - especially on a hard surface. On the other hand, I found that if I go to the gym and do stuff on machines, that involves smooth movements, not jerking my head around, then I can work out just fine. I didn't have a cardio-problem with working out. I had a jerking my head around problem. Once I stopped jerking my head around, working out was fine. So, cycling or cycle machine, cross-trainer, where your head is pretty much in one position, this stuff I didn't feel was doing me any harm.

Anyway, if you have to work out, I would definitely make sure that you can do so in a way that doesn't jerk your head around. If your workouts make you "get groggy, tired, and a headache", I think that you risk prolonging your symptoms or even making them worse.

All the best,
CS