Definitely see a doctor.

I did not get a period for a year in between college and law school. I lost 60 pounds and was running regularly. I actually enjoyed not having a period, but learned later that it sets you up for bone density problems. Your body needs that hormonal cycle to allow your bones to absorb calcium. I wish I had known that then.

When I stopped losing weight (my weight just stabilized at 60 pounds less than I had been - I was never "thin", but healthier than I had been overweight), my period eventually came back.

I don't think it's that uncommon, and I don't think it means you are not "healthy" but only your doctor can really answer that.