The way you hit your head both times , could have easily misaligned the C1/C2 ( atlas /axis) , upper cervical..
MDs don't really look for that at all issue unless it is glaringly obvious on standard imaging.., upper cervical care /chiropractic might be worth checking into..
Plus the old stigma bias against chiropractic care..
Up C Spine - more info

Possibly could be some trigger points in and around the neck & upper back muscles referring symptoms of headache & dizziness..
Evaluation by an advanced PT with knowledge of PCS & TrPs might be beneficial..
Some knowledgeable chiropractors may be skilled in that too.
I posted links for trigger points in a recent thread here, or click my username and see past posts to find it.. or just web search it..lots of info and some self care /how to do some of it yourself..