Pinch like pain - 6dpo 😬

Sarah
So my periods have been all over the place since stopping bc in September - no period at all in December. 
Started opk last Sunday (1/17) and a test line came up straight away - I've done a opk everyday since and had no lines since. My theory is I ovulated around 15/16 and missed the opk line? According to Glow and Ovula I should be ovulating today but having definite negatives on the tests. Had cm 19/20 but still no lines.
Today I've had one episode of right sided stitch/pinch pain - came from nowhere and lasted a couple of minutes. Wondering what that could be?! 
Any advise on anything greatly appreciated! Xxx