"I'm 15 years old." - If that is true it is no surprise that it has no effect on you. You are doing long-term damage to yourself if you are eating too much sugar, but it would be very unusual for you to notice any effects while you are still a teenager. Most of the damage you have done to yourself so far is probably even still reversible. The biggest problem is that you are creating bad habits. It is a lot harder to stop eating sugar when you are older than it is to do when you are younger.
If you continue to eat a heavy sugar diet, you will probably start to notice some minor effects in your 30's that you may or may not realize are related to your sugar intake. You may lose your gallbladder and maybe even your liver. You may also overtax your thyroid. It will likely start as hyperthyroidism followed by hypothyroidism. When you get into your 50's and 60's you will likely get diabetes. You may lose your toes and maybe even your legs to amputation. You may also have a heart attack and may have to have quadruple bypass surgery. Or if you have a particularly strong metabolism it may not happen until your 70's.
These are just the things that have happened to my family members from an addiction to surgery. I'm sure there are other possible outcomes. I'm sure right now it may feel like forever till you will turn 50, but when you turn 50 you may find that you would give anything to go back to when you were 15 years old when you could stop all of the damage before it is too late. To be clear, even now you are probably doing damage, it is just beneath the surface where you aren't noticing it, and it isn't as big of a deal right now because unless you are REALLY extreme it is probably still reversible. But I wouldn't take comfort from that.