Hi!

I've had PCS for years now (I'm 28). From 14-22, I had gotten concussions but had recovered after some time. After 22, I haven't been able to recover, and I've been sensitive to head bumps ever since. Able to work my desk job and able to lead a fairly normal life, aside from periods of feeling very tired and spaced out after head bumps.

Anyways, I had my bachelor party that my friends planned for me. I didn't get drunk (had 3 drinks across 6 hours), but we started out by going axe throwing. Basically you grab a heavy axe and throw it over your head at a wood target. I threw probably 25 axes over 2 hours, and felt my head shaking around. Afterwards I got that spaced out, slow thinking feeling with a headache and still have it today the next day. Can repeated shaking like this be damaging? Thanks.

Probably not any head injury or re injury... but that is a lot of repeated effort for neck/shoulder muscles..
Do they feel tight or sore at all?
Sometimes it is hard to tell if they are slightly affected already. by any sort of whiplash or if neck/shoulder were involved in the past injuries.
All those muscles can tense up and make for many symptoms..
*esp if you mainly do deskwork for job..* RSI can be a factor also..

I would try to do some general muscle strain home care on neck/shoulder muscles.. OTC for pain/inflammation, heat/ice, massage if you can do it or get someone to do that
maybe even some trigger points developed, you can google for how to check & do self care for those too..
here's some info-
Trigger point information {TrPs} for short

I agree with Jo*mar. The motion of throwing the axe causes a whiplash like motion as you let go. The upper neck is a big cause of symptoms.

Thanks! Good to know. Is it possible that this kind of shaking can cause damage to my brain as well?

No. That question is just your anxiety talking. Tell it to go find something else to worry about.