I've been trying to figure out when I ovulate, thought I had it figured out with little signs (DC, strange dreams, headache) but when I use OPKs I've not yet had a single positive. This month I was supposed to O (accord to my app) on June 26th. I got sick around this time (flu-secondary bacterial tonsillitis) and was on antibiotics. I tested and got a negative. My period was 'due' Monday. I'm worried as I've had low abdominal pain & the doctor was asking about a history of ovarian problems in my family, and I'm waiting for a scan. I said my periods were fine, fairly regular. But now it's two days late. Could being ill really alter when we ovulate??