I started to become really tired lately when playing bball..?

yeah so im starting to practice this whole summer on bball and i always practiced for like 1-2 hrs and i would like never get tired/sweaty easily.. now i get tired after like 20 mins of playing it, i get light headed and i sweat alot.. is it because the weathers been hot lately? or is it because im not getting enough sleep? or is it because im eating to much fast food?