A week after sexual contact i had spotting for 7 days. i got my period 9 days late but the flow was heavy for 3 days then became light. next month i got my period on time but same flow. all pregnancy tests are negative. am i pregnant?

Vaginal bleeding: This doesn't necessarily indicate pregnancy. However, any new, unexplained or abnormal vaginal bleeding needs medical attention. Get professional care if spotting or other abnormal bleeding continues, including abnormally heavy periods. At your age, STDs are a potential concern -- but of course only if at risk, e.g. new partner, partner with other partners, etc.