Does cramping really mean ovulation if your cycle isn't due?

So Tuesday is supposed to be my peak day according to glow. But yesterday I cramped all day. Very slight that morning but by bed time it was like my cycle was coming on so of course I bd. I have been feeling like glows predictions were a little off because my cycle always comes a little before or up to a week after glow says af should come. So I figure maybe yesterday was my peak. Thoughts?

I'm not using opks because I promised my so I would lay off all the spending 🙈