Weird period?

We are just now officially TTC and I took my last BCP on Sunday. Usually my period follows on Wednesday like clockwork. This time, no period. However, Friday I get a very light period that has now went away. It wasn't enough enough for a quarter of a regular tampon. So I took a test, and it was negative this morning, Saturday morning. Is this just a weird period or should I test again next week? 
PS I had an "a-ha" moment when I remembered I took 7 days of antibiotics this month.....but I can't remember the days we had