Is it normal for a 16 year old to have a 42 menstrual cycle? I used to have a 30 day cycle until about 2 months ago

At 16 your body is still becoming accustomed to having a period. It can change frequently for years before your body regulates itself. Then your body should settle into a more normal cycle.

It sucks because you never know when you're going to get your period, but trust me, this won't last forever.

When I first started getting my period I could go months with nothing, then have a period twice in one month, for 7 days!

My period really wasn't predictable until I was in my 20's.

If you're worried, talk to your doctor, but really, this is normal in your teen years. :)