I'm a week late, but my last 3 periods have been ranging from 17-54 days between cycles. i had protected sex twice. could i be pregnant?

Pregnant: doubtful if concerned take a home pregnancy test

Irregular periods: Irregular periods are one of the most common problems obgyns treat. If this is one time problem it usually resolves on its own. If this is a recurring problem you should be evaluated. Infections & hormonal changes can cause spotting. If there is a concern for pregnancy then do a home pregnancy test . There are many options available to help regulate the menstrual cycle. Schedule a visit.