Serious question. Ok I'm 15, 6'4 and 160 pounds, the last couple months i had problems coming and a reduced...?

drive, so I was pleasantly surprised when yesterday I masturbated and it was hard as hell and nearly 8 inches long, and I was more "horny" as girls say. What could have caused the 1-3 month..."disfunction" I mean i could still but i wasn't as "hard".