Kinda TMI, no picture though!

Heather • TTC #2, for 5 years
I had my period last week & I usually have the dark red discharge a day after it, or nothing at all. I had sex on the last day this time & I've been having a lot of brown discharge ever since. & its been like 5 days. I always have sex on my period, this has never happened though. Opinions on what it might be cause from?