I fell on friday and hit my head on the concrete, and now have a black and blue eye. today i started feeling a little light headed. should i see a dr?

Yes: Yescyes yes. May be concussion or worse don't procrastinate.

YES, See a doctor: Red flags after a head injury that mandate seeing a doctor: black eye/ raccoon eyes, bleed from ear, waxing ; waning alertness/ drowsiness, persistent nausea w/ or w/out vomiting, dizziness or vertigo, "worst headache of my life", unequal pupil sizes, new neurological deficits, or any symptom that you think should be checked out. Good luck!