Hi there are Herbal Med's out there for you to use and harmless , Please ask at your Local Pharmacy they will do there best to help you out , Take care ,
I do think you should go to a doctor. The doctor may or may not prescribe sleeping pills. He may treat your leg pain or some other medical condition. Whatever it is, at your age, it is VERY unlikely to be life-threatening. There's no point in your suffering when this is likely something that can be treated and cured. Do you have a school counselor or school nurse you could talk to if your parents absolutely refuse? Sometimes another adult can communicate with parents on behalf of the teen and be more effective. BTW, 4-6 hours of sleep is very low for a teenager, but many get that little sleep from their lifestyle choices. However, it is not healthy in the long run and should be evaluated by a doctor.
Also, those herbal meds are not without risk and should not be taken long-term without medical supervision.
Try melatonin 3 mg tablets, you can get them at your local drug store