Why is it that every day after school I have a huge urge to ejaculate. If I don't, pictures come up, and I can't control it. I am able to not think about dirty things while I'm masturbating. It's just the desire is so strong every day. I can't hold it for more three days and that was terrible, I was so uncontrollable of my thoughts. Do I just have a high libido or whatever it's called?
Part of the reason is habit, part of it may be opportunity (I assume that your parents work and you are alone for a little while after school), but mostly it is just a fact that young men both produce a lot of semen and that their seminal vesicles are not fully matured, so there is less storage space. In addition, your hormones are very high because of your development and are unsteady. The result is that your production of semen is high and that translates into a high libido.
Your sex drive is higher now that it will be in, say your thirties or forties, but it is not unusually high for a teenager. In fact, what you are experiencing is fairly typically for your age. The reason it hits you at this particular time is more from habit.