Bleeding during first month of the birth control pill??

So I’m new to taking birth control and I just finished the 3rd week of pills. I stated taking them on a Sunday and it was the first day of my period because my doctor said I could. I started bleeding about 4 days ago and it’s still bleeding but not as heavy. Is this just my body trying to get used to the pill? I’m not due to get my period until about next Wednesday. I just wanted to know if anyone has ever went through this as well!