First, you shouldn't be taking pills not prescribed for you. Also, did you take them from your parents or did your parents give them to you? Either way, stop doing it that way and see a doctor about the sleep problems. That all being said, I take prescribed sleeping pills and I take more than the recommended dose for women, but it's the dose prescribed by my doctor and she's okay with it because they don't make me crazy. They do work horribly for some people though. Medication is a pretty individual thing and best to work with a doctor.
Anyway, especially if you are concerned about the low dose not affecting you, it sounds like you have legitimate sleep issues. Or this is not the right medication for you. It's worth seeing your doctor and getting your own medication if that's what s/he thinks will help. Can you ask your parents about seeing a doctor instead of taking their medication? As for not needing them or getting dependent, just stop taking them, especially if they do not work...don't take more of anything without checking with a doc, and especially if it's not prescribed to you to begin with. Meds can be really touchy with ever-changing adolescent minds and bodies...really important to have a thoughtful and smart doc.
If you don't take them, you might not sleep well, but only you can gauge to what degree that affects your daily life. Having a routine in the evening, staying out of bright light or away from computer/I-pad screens for the last hour or two helps. So does exercising earlier in the day. Good luck. I know not being able to sleep (and/or nightmares and other sleep issues) really stink.