Horrible pain at 9 DPO!!

So according to Glow I was supposed to ovulate on the 3rd but I felt the ovulation pain on the 31st instead so just a few days before. Everything was going fine until today. Last night I went to sleep with a headache and woke up with it so I just chalked it up to it being AF next week. But then today just only an hour ago, I started getting cramps and then the worst cramps I've ever had in my life. Right in the center of my pelvis all the way down to my vagina. It went on like that for about 10 minutes. I don't know what's going on with me. It definitely got better but why am I having pains? I'm due for AF on the 17th according to the APP. I define try had sex in my fertile window so I'm not sure if it's implantation cramping that I am experiencing. Please help!