Hi I Was Wondering If You Could Help Me Out

Hi I was wondering if you could help me out I’m 14 year old and I started my period when I was 11 and these past couple of months it’s been staring exactly 4 days earlier every mounth so like last month it started the 30 th of April and the month before that it started on the 4 th or March I’m really worried about this please help I went to a doctor and they said don’t worry it will regulate it’s slef out.