Amphetamines help ADHD?

Hi, I've been diagnosed with severe adult ADHD. As a teenager I tried meth and it really seemed to calm me down. I could concentrate, focus and even sleep on it. (I am in NO way trying to glorify methamphetamine. It is an awful life destroying drug.) The doctors can't give me ritalin because of my history of substance abuse but I reccently started taking phentermine for weight loss and it really calms me down and helps me focus among other things. From what I heard phentermine is an amphetamine. So my question is, am I just crazy or do amphetamines really help ADHD?