What Causes Headaches With Syncope And Breathlessness?

i am 17 years old pretty much all the time for the last couple of years i am always light headed i feel very weak and especial when i lay down on my bed but i am awake watching TV i get up and feel as if i am going to pass out plus i always feel out of breath and get headaches all the time in the frontal part of my head and in the middle please tell me what i should do?