I started taking amphetamine about 3 weeks ago, i started low with like 20mg since i dont know how pure it is, then i took a break for 2 weeks, and last week i took it about 3 times at 24-30mg and the first 2 days i could really feel how it helps me concentrate at work and made me feel really woken up, but now i took 30mg and suddenly it doesn't feel the same anymore, what could cause this or should try taking it orally instead? I really enjoyed being able to concentrate on my work for 8-12 hours 
