21 day pill

Hi girls, i was wondering if any one in similar situation. Started my pill last monday, three weeks after having my wee girl, ever since starting it i feel my mood has changed and feeling a bit down and hormonal but before starting it i was feeling upbeat and good. Its the same pill i was on before i started trying for a baby and was on it for a few years. I noticed when I was pregnant i had less worrying and anxiety than i did before i fell pregnant, just wondering if its all connected? Any advice or stories would be great thanks