Hit top of my head really hard in concrete 3 days ago, felt really weird and still feel weird, no nausea/loc/other symptoms, can i have a concussion?

Get checked out: The symptom of feeling weird is pretty nonspecific, and while may sound benign sometimes can be a signal to something not so benign like a brain bleed. Depending on your age and your other medical problems this could be either a post-concussive symptom or a sequella of a small brain bleed. Talk to your neurologist if symptoms are persistent to see if MRI brain would be warranted in your case.