Emergency contraception but I am already ovulating?

Other than Ella, then your only option is to have a Paragard IUD fitted within 5 days/120 hours of the unprotected sex. That can stop the pregnancy implanting, although it's not guaranteed.

Are you actually in your ovulation hours, or just in your fertile days, leading up to actual ovulation.
You have up to 5 fertile days, then your hours of ovulation after those. Plan B & Ella may still work during those days, although the only contraceptive pill proven can prevent pregnancy during the 24 hours around ovulation, is Ella.
If you're not sure, as you're just relying on an app/website (which is just a guide), rather than an ovulation test or charting your fertility symptoms, then it may still be worth taking Ella. Ella can prevent pregnancy even if you're within the 24 hours around your actual ovulation, so it could be worth a try.
I think, if it were me, I'd b using Ella & getting a Paragard IUD fitted, to be safe. If that's available to you. If you're actual in your ovulation hours, then I'd def suggest using Ella & the Paragard IUD, in case Ella fails. You can go to the Ella website to see what I'm saying about it possibly working during the 24 hours around ovulation itself. It's not guaranteed, though. That's why I'd try both. The Paragard IUD can also stay in place as longer term contraception, if you get on ok with it.

IUDs can give cramping if you've never had a baby before. Some women feel them more than others. May be worth a try if you're desperate to avoid pregnancy, though.