If my head hurts when i do mental activities and not when i do physical activities, do i still have a concussion?

Yes very likely: A concussion is a brain injury, so just as activity/work on an injured ankle would cause ankle pain, activity of the brain (whether from physical exercise or mental work) can flare up concussion symptoms. I advise patients to rest from homework, studying, reading, watching tv with lots of action, computer, texting, etc. I recommend rest from most activity until symptoms w/schoolwork, etc are gone.