I have been taking ADHD stimulants my whole life. I am currently on Adderall (dextroamphetamine and racemic amphetamine) and I am conserned it is stunting my penis growth. I'm 5.5 inches not grow?

No, it's not . It's probably the last thing you want to do, but if you get a thorough physical exam from your primary care doctor, (s)he can tell you what tanner stage of puberty you're in & talk with you about seeing a pediatric or adult endocrinologist, depending on your age.There are specific measurements they use (none of which hurt you) & they have growth charts for just about every part of the body.
Not possible. Adderall (dextroamphetamine and racemic amphetamine) has got nothing to do with penis growth. Penis size and growth is dependent on your genes and race. A lot of teenagers are worried about penis size, your size is just fine and in normal range. Don't try to measure up to guys in the porn movies, those sizes are not normal.