Hello, Im 21 Years Old Male. I've Recently Found Brown-reddish

Hello, im 21 years old male. I've recently found brown-reddish stains on back side of my underwear when i woke up, im experiencing this for 3 consecutive days. I've checked my stool & urine but there's no sign of blood in it & i dont feel any burning sensation when going to pee or poop. Im freaking out! Don't know what to do! I don't even drink or smoke neither i've sex with someone. Im having thoughts that this is the end of my life's journey. Please help me out! I don't know what to do how to tell my parents about all this. Please help!!.