Girls, hello! Excuse me for the details... Six months after giving bi…

Girls, hello! Excuse me for the details... Six months after giving birth, my period came back. Everything went well, just like before, five days of normal flow, even without pain. According to my calendar, ovulation is on the 10th. And today is day 18 of my cycle, and I noticed brown discharge on my underwear, like at the end of my period. This has never happened before. Should I be worried and see a doctor? I had an ultrasound three weeks ago, they said everything was fine, everything was already restored. We're using protection with my husband, everything is okay, we're not pregnant.