pingpong,

Welcome to NeuroTalk. You have a wrong understanding of sub-concussive impacts. Sub-concussive impacts do not cause any symptoms. The danger from SCI's is the cumulative effect. Those dings that had symptoms but cleared quickly were concussions.

Regarding the ping pong ball hit. I doubt the hit did any damage but more likely you jerked your head in response. A head jerk can easily cause concussion symptoms.

I wonder if you have done something else to cause your symptoms. Have you fallen asleep with your head and neck in a bad position ? Neck inflammation can cause a myriad of strange symptoms.