Period is always late

katie

my period is always late by a month at least for instance it was 48 days late this time but i talked to my doctor about that and other things so she decided to test me for the other things and that. I got an ultrasound done but nothing was wrong. The doctor said the test came back fine and that was it. What could possibly be wrong that makes my period so late?

(i’m not sexually active btw and i’ve had my period for 4-5 years)