I've come off my period had sex with my big the next day now i'm spotting? what does this mean - he did cum in me by the way

Spotting: 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.

Cervicitis? STD?: If your period ended only 1-2 days before, it may just be a bit more menstrual blood. However, non-menstrual bleeding after sex often means inflammation of the cervix and can be caused by STDs like chlamydia and gonorrhea -- and all sexually active persons your age (17) are naturally at high risk for these STDs. See your doctor ASAP, or your nearest NHS GUM clinic. Good luck!