ADHD - 17MALE - Suggestions please as ma

Question in the end, please read if possible or you can skip Since I got diagnosed with ADHD, I have been prescribed 5 mg methamphetamine, then later properly re diagnosed by AIIMS and dosage increased to 20 mg tablets. I feel a drastic change in my focus and I am able to do it without any distractions, but the down side is whenever I take these I get easily irritated due to a  strange feeling that exists makes me feel uneasy at rest as well which is not physical and I can't describe. That is fine though, but AIIMS recommended an increase in dosage as my weight satisfies it but I hesitated for now. 20 mg doesn't last long and according to prescription I have to take again total 2 times a day. ( Prescribed according to my requirements ) Now here is my question, I have done research on amphetamine, and the duration of work plus effectiness is more than inspriral 20 mg. I want to discuss this with my doctor but my next visitation is after 2 months. I would appreciate as many answers