My Period Is Now A Week Late. I'm 30, And

My period is now a week late. I'm 30, and sexually active however my husband had a vasectomy 16yrs ago so I know that rules out pregnancy. I'm having pains in my stomach especially on my right side (near the belly button area). It's starting to worry me cause my periods are always regular (last month I was a few days late as well).
I'm starting to worry now.