I got my period for 9 days light but not spotting at first then it gets heavier but it doesn't fill up the pad at the end only brown period came out. i took many pt all of them are negative. is this pregnancy related or is this normal?

It can be normal. Periods can vary a lot between people and even with the same patient. What stress you had over the month before your period, whether you were getting enough sleep, how much exercise, what climate you were in, what you were eating and many other things can affect your period. It is best to watch the pattern and see if it is consistent each month. Also get a regular Gyne check up.