My head feels light But doesn't hurt I need help.?

I don't know what it is but my head feels really light, i doesn't hurt at all. At 1st i thought it was i wasn't having enough water but i drank a big bottle of water. So that didn't help so i thought i wasn't getting enough sugar but that's no the case either. I eat meals, fruit and veg and all that's stuff so its not malnutrition. Can anyone help me out cause i hope its not serious (Im a 15 year old male if that has any relevance.)