So difficult

Ok so I'm using the glow app and this month decided to track my ovulation, I used opk and am currently on cd 17 and haven't got a positive! I got a slightly darker line on cd 7 which I though was waaay to early, then I was having cramps and aching on Sunday which I was supposed to ovulate! And again today I'm aching and cramping but again all negative opk oh what's going on :(