HI, Im A Student In College. I Recently Missed A

HI, Im a student in college. I recently missed a period and am sexually active. I am on birth control and took them within two hours of each other every day consistently last month. My partner and I did not use a condom until he had to finish. during the time of the missed period I was about to leave for college and very stressed. I haven't been feeling that fatigued, but I have been a little nauseous, which may be attributed to the anxiety. I have generalized anxiety disorder and not that much money so I can't afford to take a test every time I'm scared. Do you think I have anything to worry about?