Have you tried exercise yet? I bet the biggest problem with Judo will be the exertion bringing back your symptoms. And I don't know how you feel, but for me the thought of thrashing around on a gym mat sounds like something I would avoid. Makes my head hurt thinking about it. Of course I have some vestibular issues, so I'd probably end up throwing up everywhere pretty quickly...

You should probably also consider the long term risk of further sub-concussive impacts. I'm an athlete myself, so I understand wanting to get back to sports, but I think the risk is worth some careful consideration.

I also feel better than I did 2 months ago, but every time I try to ramp things up too quickly I find myself regretting it. Just a heads up. For me at least, it's really hard to figure out what is too much. My symptoms tend to creep up on me out of nowhere a day or two later.

You do wear a helmet on your mountain bike right? I know there are some Snell certified mountain bike helmets that meet very exacting standards. I would look into those.