GAH...I have this same problem too. Sometimes I would go for maybe 2 months without my period. My doctor and I (I'm 14) have talked about this and since it's almost 2 years since gettin my first period, she said after the two year mark, if it's still irregular, we'd do some blood tests. (And I don't really mind not getting my period, cause I hate it too!
) Have you talked to your mom about it?