My period is irregular since my first time come(14 years old)

The irregular period normally continuely 2 months bleeding but not heavy, then eat control birth pills to stop it.

I check every year by Ultrasonic B, Sex hormone, the doc said they are all normal, no tumour, no cyst, endometrium is normal.

My doc also ask me to eat a period sex hormone, but after several months it come again.

During these 2 months, it is lightly dark color, sticky,

but just a little, lasts around 15 days, and normal bleeding 15days and then stop 1 or 2 days, but continuelly bleeding lightly with fresh blood till now. Actually every 1-2 years I have such similar things happend, and each time I eat the birth control pills to stop it, such as norethindrone or diethylstilbestrol. But after 1-2 years, this situation come back again. I hate of eating birth control pills, it is bad for health, will have some side effeect to uterus, right? I haven't pregnent before.

What can I do? Is there anyone can help me? I am 27 years old, it's so frustrated and exhausted, I want it normal in my life!!