Help!

So I started my pill on New Year's eve as I had to start it 'when my next period started'. Usually I'm on my period for 7 days but it's now the 4th day and it's stopped. Obviously I am having sex with my SO as I'm on the pill. I'm not sure if this is just natural when you start the pill or are on the pill or if I should be worried about pregnancy or whatever. I'd rather avoid getting myself checked out if I can. Can anyone tell me if its normal or not as I'm becoming a little bit concerned😁