Hi there and welcome. A normal period is between 2 and 7 days. You are just outside of normal with an 8 day period. Not something to be 'too' concerned about especially if day 8 is more like brown discharge than true bleeding. Now, I do encourage you to talk about these things with your mom This is something that helps to have someone that you are close to to just run things like this past (even a big sister, older cousin, aunt, etc. is great to use as a sounding board). Right now, I'd say this is not something to be worried about. If the days of your period get longer, then talk to your mom to see if she thinks you need to have a pelvic exam. good luck
Ive had my periods for 1 1\2 years now ad i get mine for a week some times longer