Tightness in head and dizziness

I am 15 years old and for the past 2 weeks my head has been feeling very tight and it makes me a little dizzy. My vision is also getting kinda shaking and weird.. it's hard to focus on some things, especially if im just standing still I've been to the doctors once to get it checked out but they said im just stressed out, but i havnt been stressed out at all. In fact, lately i have been care free! i don't know whats wrong and i'm starting to get scared. what's wrong with me?