where's AF??

Charlotte
I haven't had my period since the 4th January 2017 (usually 48 day cycles) Funny coincidence as this is the month my partner and I decided to TTC. Every few weeks I get the signs my period is coming (pimples, mood swings). 
One day last week I had a fair amount of dark brown/red spotting and I was so happy as I thought AF was finally here!! But after that one day last week....nothing at all. We are still TTC and I'm wondering if this could maybe mean we've succeeded. I did a Test the next day and that was -ve. Has anyone else experienced anything like this??