Yes. I don't know about "concussion prone", but there is evidence that shows that athletes who sustain a concussion are more likely to have another concussion. The effect of repetitive concussions can be very serious.
Possibly. A person can certainly be 'accident prone.' With each successive concussion, it lowers your threshold to have another one, especially if your haven't fully recovered from the previous concussion. ITs best to get evaluated, especially if you're still having dizziness or balance problems that may cause you to fall down a lot.
Yes. Researchers are just now evaluating why some people get concussed and others don't with the same amount of trauma it seems that certain people are more susceptible to concussions. Risks for concussions include young age, history of add/adhd, learning disabilities, migraines, and genetics. If you suspect a concussion, rest and see your doctor.