Brownish discharge

Brianna • I am 28 with a 6yr old little girl named Madelyn. Also, engaged to a wonderful loving fiancé, Ryan. TTC #2
I ended my AF 3 days ago and today I had a few times brownish CM in my panties. It started the day after me and my SO had sex.  Any idea or suggestions? Anything I read said old blood but want opinions on what you ladies think! Anything is much appreciated. Xoxo