Is it my period?

My cycle has been pretty much regular and my period was due on the 26th according to my glow app but then I got some light bleeding on the evening of the 27th and nothing the next day, had some bright red spotting this morning (29th)but nothing since. I've never experienced a period like this before it's always been heaviest on the second day. I am not experiencing any pregnancy symptoms. What could this mean?