Indeed, 15 years old shouldn't use any drugs. Not going to moralize anyone. You should read this thread more careful, and maybe it makes you rethink about you're choices.
Only maybe 1 in 1 000 000 can use strong opioids every now and then for long periods of time, little by little you get addicted by doing it more frequently, finally you think what the hell why doing only 3 days a week why not 4, 5, 6 hell why not all the time? I could use them 8 years without getting addicted used every now and then binged on them too. Someone might use 10 years, but if not stopping completely I would say 99% will end up addicted and then there waits hell. Slowly but surely you find yourself turning to opioids every time when you have problems in life or having a negative emotions that you want escape, like anxiety or depression. Mild opioids like codeine and tramadol can be also hard to handle because for opioid-naive person they work very strongly, I would say I got as much euphoria out of tramadol and codeine that I did get from oxycodone later one, after turning to stronger opioids the milder won't work anymore. And oh when you get some strong wd's you really feel that you fucked up to the point of no return. However this why around 50% of addicts will end up in life long opioid maintenance treatment.