I think my ovulation is off....

Brianna

As I mentioned before I had spotting for two days straight and I looked online and it said it was ovulation. I had sex on one of those days (the 27th of November) but glow said i was suppose to ovulate the day after the last day of spotting. I’m now cramping in my lower abdomen and back. (It’s on one side .... and the middle). My question is how accurate is glow ovulation predictions? Do you think it can be implantation cramping?