Little to no period this month?

my first menstruation was arnd 11-12years old, currently i m 18. sicne my first period till now, there has nvr been once ive had such a weird period. well as usual, my periods were roughly around the same day each month, sometimes 1-3 days late, sometimes 1-3 early. this month no exception. but since the first day, my period has been really little. i could check my pad 8 hrs ltr, and there would just be a drop on it, and its dark brown close to black. im really worried n hoping if someone noes what is this bout. i cant go see the doc because im afraid to let my mum noe. pls help.