I was a dancer (no, not .T.H.A.T kind of dancer) for over 18 years, and my periods were never regular unless I was on bc. And, yes, it was due to the exercise I got. However, the most I ever skipped was one month at a time, and that didn't even happen but once a year or so.
I'm not an expert by any stretch of the imagination, but I would think that not having a period for over a year isn't normal. If you're ttc and not having your period (or even if you're not ttc), I would suggest seeing a doctor about it. Have you not spoken to an obgyn about it before? Like, during a regular exam or something?