Sounds like the Nexium 40mg worked better for you than the Prilosec 20mg does.
Not all acid reflux medications are alike. For a possible fast remedy, try taking Prilosec 20mg 2xday instead of just once. One in the morning when getting up and one in the early evening. Your doctor will tell you it won't hurt you to try it. Otherwise, call your doctor and see if you can go back to the Nexium. Good luck with your insurance company though. Mine only pays half the cost so I'm stuck with $175.00 a month, minus the $50.00 discount I get with the Purple Card that Astra Zenica (spelling?) offers immediately on-line.
Unfortunately, with all illnesses, you go through a trial and error period where you try "everything in the medicine cabinet" before you find the "magic pill" that works for you. I've had AR for over 20 years and I've tried them all.
If I didn't have humor to help fight the disease, I'd spend the rest of my life in tears.