Regular cycles but im 7 days late with negative hpt 2 days ago. treated for std 2 days ago as well still no period. preg? other health problem?

Normal variation: For a woman who usually has regular periods to occasionally be late or early with a period is common and is usually just normal variation. Sometimes hormones are off and she will totally skip a period, but if they come back regular likely not a problem. If periods get more irregular then could be a thyroid or prolactin problem, stress, gaining or losing weight as a cause, for instance.