Brown blood

Okay yall I’m 15 days from my period, they are very regular as in my period always starts within 1-2 days every month. I’m on the pill, Millia. So I had brown blood in my underwear earlier, no red just brown. I’ve never ovulation bled, I don’t mid cycle bleed. It’s the same every month. Why am I having brown blood/discharge 15 days before my period? Should I go to the dr? I wish I had a picture but I was so aggravated I just didn’t take one. Thanks yall!