Normal for my cycle to change?

I was 18 when I went on the pill, now I'm 22 and still on the same medication. But within the last 6-9 months, the day I usually get my period has changed by a day. But within the last few months, they've been coming a few days earlier than normal and I've had spotting between periods. Is this normal? It really freaks me out and makes me think I'm pregnant even if there's no chance in it...thank you!