I have missed my period regularly, recently it has been 5 months and still no period. The doctor told me I haven't had my period for almost 5 months, what is the reason?

Doctor, I am 18 years old this year, I missed my period for 5 months and got 1 time. Since then, I have been counting for about 4 months without a period. I went to the doctor and they said that the egg was not ovulated, so I did not have a period. The doctor asked me if my period is often 4-5 months late, is it a concern?