As time goes on for women on birth control pills it is not unusual to stop having en daily withdrawal bleeding. Over time the progestin in the pill wins out and the lining of the uterus
thins beyond the ability of the low-dose estrogen
formulations to produce enough thickness to cause withdrawal bleeding.
There is no reason to be concerned. The Pill is effective for contraception
if taken daily regardless of whether or not you're having a withdrawal bleed. There's nothing building up. Prior to the industrial age, what was natural is for women to be either pregnant or lactating most of the time and to have very few periods at all. Relentless menstruation
is an entirely modern phenomenon and not always beneficial. If the pills work well for you-feel free to continue them through menopause
I hope this answer was reassuring. Thank you for your confidence. Feel well.