Long winded question...

Ok so my last cycle was from May 2nd to May 6th. According to Glow I would have ovulated around May 18th/19th. I did the BD every other day during my fertile period before my fertile period and after. Now I'm not supposed to see AF until June 2nd, so can someone tell me why am I having light spotting and light cramping today, 5 days before my cycle is supposed to start.