Can you tell me what this means?

I am 15 years old... I love going outside with my friends to hang out and all but whenever im in the daylight, even when cloudy, I get headaches and feel that i have lost a huge amount of energy. Then as a conequence of going outside by day, I feel terrible painfull headaches later on when a bit darker... I also feel like I cant understand some things that people feel... Whenever I see blood I feel a little scared but I also feel strange, as if I wanted it... I get so scared sometimes... What does this mean? Do I have some sort of disease? if you want more details or chat: nainaichuu@yahoo.com