I'm 16, almost 17 and I was previously on the pills for the last years, not due to me being sexually active but of severe period problems. A few weeks ago I switched to the shot and my doctor told me I could expect anywhere from 5-20 pound weight gain and with my previous birth control I knew she was most likely right but since starting it I've lost five plus pounds and I was just wondering if it could be from my switching birth control or maybe something else is wrong.