Weird Experience, Opinions Please!

Ok, so yesterday morning, the 4th, I was woken up from a deep sleep to some pretty intense cramps and lower backache almost like what I get when it's about time for AF except I'm not due until the 15th. My cycle is about 25 days. I rushed to the bathroom and nothing. It went away after I laid back down. According to Glow, I should've ovulated on Monday the 1st. Any idea what I could've possibly experienced? It kinda freaked me out!