Please help!!

Hi all
I'm so confused..
I had my period on 3rd August and my cycles are short 21 days. So due 24th August.
So later in the afternoon  in on 24th I had had brown stringy discharge (sorry tmi) which on lasted the day. Had nothing since.
I'm so confused was this a period or not? Did a test Bfn.. Me an hubs have sex every other day to increase chances.
Any advice??