What can young men do against sexual temptation when it builds up so strong? Does it ever get better or easier? Like I'm even willing to wear a chastity device as a reminder to myself to keep it all under control.
One aspect of the matter is to realize that as a male you will be dealing with these temptations for the rest of your life. You don't need a chastity belt. You need to develop your self-control. "No temptation has overtaken you but such as is common to man; and God is faithful, who will not allow you to be tempted beyond what you are able, but with the temptation will provide the way of escape also, so that you will be able to endure it" (I Corinthians 10:13).
What I tell all young men is that you cannot trust yourself to resist sexual temptations. Once you are heavily aroused, your judgment is hindered (you don't think clearly). Thus, it is better not to get into arousing situations and tell yourself you can stop because you might not. "Do not enter the path of the wicked and do not proceed in the way of evil men. Avoid it, do not pass by it; turn away from it and pass on" (Proverbs 4:14-15). This also is the reason you need to stay away from pornography. It fills your mind with inappropriate images and ideas which will more than likely lead you to do inappropriate things.
Another point to remember is that your body needs to ejaculate once in a while. You are constantly producing semen and you can only store so much before some of it has to come out. If you try not to ejaculate, the pressure rises and your desire for sex rises as well. If you wait too long, instinct will try to take over so you can ejaculate. The better way to handle this is to masturbate regularly or allow yourself to have wet dreams or both. Regular ejaculations will keep your urge for sex at a manageable level. Don't use this as an excuse to look at pornography -- that remains wrong and it doesn't solve the problem; instead, see ejaculating as a bodily function, like using the toilet. When the need is there, relieve yourself and go about your daily life.