I'm 18 years old and I get my period every 2-4 months and lasts for either 3-4 days or a week. I had my period when I was at the age of 11 years old and the elders told me it was fine and normal but when I reached the age 13 I asked my Science teacher if 3-4 months before I get my period is normal but she told me it wasn't normal and advised me to appoint a personal check up with an OB Gyne doctor (female) to check up on me she also told me that I might have difficulties being pregnant or bearing a child in the future.