My period is usually no longer then 5 days! this period is going on day 8. i'm active during this period, could that be why it's so long?

Nobody's perfect!: Even women with very regular cycles will occasionally have a weird one. I doubt it's related to activity. More likely it's a result of hormone variations or external factors like stress, medication effects (aspirin included) or other temporary influences. Rarely a very early miscarriage can cause this.. See your gyno if heavy bleeding continues.

Possibly: A lot of different things can affect your cycles and your periods, and a change in your level of exercise is certainly one of them. This is still not abnormally long. This may simply represent an isolated "hiccough" in your cycle but if this becomes a recurrent issue, if it doesn't stop in the next day or so, or if you get additional symptoms you should be checked out.

Menstrual flow: Duration of bleeding can vary cycle to cycle. The fact that you were sexually active during menstruation could give the appearance of longer, heavier flow as menstrual blood would mix with the ejaculate. The color would also give some insight. Is it bright red: active free flow. Dark red or brownish: old blood, no longer active flow. I would simply keep track and if persists seek evaluation.