Currently on 2 x 20mg Omeprazole and Dymista nasal spray (Fluticasone/Azelastine) for PND and LPR. Can I take oregano oil and probiotics also?

Yes. There should be no problem taking these products in combination.
Mgt. You can take both of these in the usual quantities.Oregano oil is not a tested medication. I would suggest eating well before bedtime, limiting alcohol/ caffeine and sleeping with an additional pillow. If these measures are not helpful your medications may need an adjusted dose.