I Was On Adderall For About Two Weeks Taking Two

I was on adderall for about two weeks taking two (pink pills, i wasn't prescribed so I'm unaware of mill.) sometimes 3 a day for diet use. I began the pills about 2 days after the last day of my period. Now it's 3 weeks later & I still haven't received my period. I'm not sexually active. So can the pills be the reason for this?