Please help! Similar experience and outcome anyone?

Hi, hope everyone is okay. New here and just wondering if anyone has had a similar experience as me. First of all I'm 28 and was diagnosed with PCOS last year. I've  had clockwork cycles since they settled when I was about 19. they are normally bang on 24 days (ocasionaly give or take a day) I was due on, on monday but mother nature never showed up, i have felt like i am coming on with mild cramping lower belly and lower back for about 3-4 days now. me and my partner have recently ditched the contraception as we feel ready for our 2nd child although we aren't 'trying' just going with the flow. We had sex on Sunday (the day before due on) and the last time before that was just before my last period. I have taken 2 tests just in case, both negative. If I'm still not on towards the end of next week i am going to book in with my GP but in the meantime if anyone has had a similar experience or any advice would be nice to hear it. I'd say its pretty unlikely I'm pregnant but this is so unusual for me and I can't help but wonder what could be going on. Thank you!!