Is it normal that your period last longer aftee you have sex when its on?

How much longer: Sex should not affect the length of your period, however, there is natural variation in the length of periods and if it appears longer following sex, the two may be unrelated.

It might: Possible, but by having sex during your period you also more succeptable to infection that may cause prolonged bleeding or spotting, so if it goes for too long, or if you get any other symptoms see your gyn.