Well, I can't say for sure because I'm not a doctor, but I can say from my own experience as a woman with periods and whatnot - sometimes (often) I feel unwell around my ovulation. It makes sense when you think about it since ovulation is yet another hormonal event, not unlike PMS or our menstrual cycle itself. If you continue to feel lightheaded and short of breath, let your doctor know. If you've recently had unprotected sense and suspect that you're newly pregnant, get an early result pregnancy test and start taking it the week your period is due. I think it's best to start testing four days from when your period is supposed to start.