Is it easier to get pregnant having sex on ovulation day?

Yes! That is the most likely time to conceive! good luck ... Although your profile says you're pregnant already, so best of luck in your journey!
Vs not having sex? There are a few scenarios to consider. "best time" to conceive is to have sex around ovulation. Because sperm can live for a few days, don't have to have sex exactly on day of ovulation, just anywhere from a few days before to after. "worse time" for conception is around/during menses b/c no viable egg. However, if you've miscarried 6 times, you need to see reproendo for evaluation.