TTC. Can taking advil 800mg once or twice a week after menstruation/or taking Relpax (eletriptan) for migraines affect ovulation timings? Any other meds safer?

These are fine. While TTC, those meds are fine. They shouldn't interfere with ovulation. However, you cannot take either of those medications once you are pregnant, so you may want to see your doctor now about getting on a different regimen for headaches.