irregular periods

Just wanted some advice whether I should be worried or not. I decided over a year ago to come off contraception due to me not feeling myself. But my periods returned to normal after couple of months and started to have regular periods. However over the past two periods they have been completely off. My last period I was 3 and half weeks late and this month I am a week late. I dont know whether that's completely normal or not just wanted some advice or maybe someone has had similar? Or is it something I shouldn't worry about?