Have you had sex recently? By recently I mean like in the last 24 hours?
Sometimes this brownish discharge can appear just because you have had sex and kind of stirred up everything in there. There is increased blood flow to your cervix which often causes a little light bleeding or spotting. This has happened to my sister so I know what I am talking about.
It’s probably just a little bit of old blood mixed with your discharge.
Brown blood is old blood and not much of a concern but bright red is fresh blood and if your bleeding fresh blood you need to call your doctor immediately.
Light spotting is quite common in pregnancy and usually nothing to worry about.
If it continues for more than two days or so than call the doctor again even if he did say that everything is fine. I am sure everything is fine though and I wish you the best of luck!