AF or Pregnancy?

Des
I doubt I'm prego but I'm curious about somethings.. I enjoy starbucks so much but today when I drank it I felt as if I was going to vomit, now I'm having horrible headaches and lower back pain for a few days... af was sappose to be here but I started working out again this month and heard that could affect af. Anyways I was just curious on what it could be