Am I masturbating too much? Can it cause me to have an early ejaculation?

Well i'm 20, and i've masterbation at least 1/day since when i was 12, the longest period that i haven't masterbated is 3 days. I do twice a day on a regular basis, rarely sometime 7 or 8. When i was puberty, i can get an erection all the time and now i don't even get erection in the morning (maybe because i masterbated everymorning ?) , sometime i cant get an erection. I dont have a girlfriend (yet), do i need to stop masterabating ? and how do i stop masterbating ? i just can't sleep without it. Also i'm 100kg , 1m75 and Asian. My friends adviced me to reduce it down, it causing me to have an early ejaculation, is it true ?