If I never had a menistration an I'm 19 how do I know if I'm fertile.

If you are 19 and never had a period... your gynecologist should have told you this long before now. Because you should have gone to one years ago... and should have been going every year.

Is this a bad thing that I jave not started yet?

is this a bad thing that i jave not started yet?

Unusual... I highly recommend going to a gynecologist for an exam and tests if you have never been to one yet.

Nobody online will be able to tell you why... but your gynecologist should be able to give you some reasons after testing.