Whats goin on??

Hey ladies, just an update. My last menstrual cycle was Dec 19. I was supposed to start yesterday and didn't. I also had sex last night and still no AF. About half hour ago, I went to the bathroom and I had a couple spots. Normally when AF starts its medium to heavy. And nothing new has shown up since half hour ago. Any thoughts? Oh and my periods are regular and have been since my youngest was born Feb of last year.