Soda, including Diet Coke, makes gerd worse. It is highly acidic and will stir up the acids in your stomach. It may work well for someone, but it is one of the first things the docs tell you to avoid if at all possible.
When looking at stomach problems, many of us forget to look at what we drink. Coffee, tea, soda, etc... are generally high in acid and can greatly contribute to symptoms.
Have you tried other proton pump inhibitors besides the purple pill? That is nexium, aka esomeprazole magnesium, and is only one of the available options. It may be worth trying omeprazole (prilosec) or lansoprozole (prevacid) or one of the rx ppi's. I have more than a few types of medications where one causes severe migraines but another does not. Bad as migraines can be, I understand if you are leery of this.
Ask your doctor to rx carafate (sucralfate). Ask for tablets specifically because there is a generic of the tablets but the liquid only comes in brand name and is expensive. The tablets can be taken with a full glass of liquid or else dissolved in a few ounces of water. I firmly believe that carafate should be in the medication cabinet of anyone with gerd symptoms. It is incredible for stomach problems related to too much acid in the stomach because it will coat the stomach completely, giving it time to not be irritated and damaged by medications, stomach acid, etc.... It is not well absorbed by the body so it works in a mechanical way by providing a barrier between the stomach and it's contents. You do have to time when you take it and when you take the rest of your medications and when you eat, but you can set your phone, computer, etc... to help. It is taken 1 hr before or 2 hours after a meal or medications.
Ginger is wonderful for your stomach. It is highly effective for treating nausea and is safe for morning sickness. you can either stir powdered ginger into a drink or food, or you can use fresh ginger. I prefer fresh ginger as it seems to work better and taste better. It is sold in the produce section near the sugar snap peas, bean sprouts, etc... At first buy a small piece, maybe half the size of your palm or smaller. Break a piece off of a larger piece if you don't see the size and quality that you want. You want it to be firm, not shriveled or moldy. It definitely should NOT be squishy. Around here the price is three to five bucks a pound, but the small piece I buy is generally maybe fifty cents. So it is super cheap to try.
To use the ginger, take a knife and cut off slices about the thickness of a dime or penny. You can peel it, but I don't unless I am using it in a recipe rather than for tea. I do wash it when I bring it home, then I dry it and store in the fridge. Put 2-4 of the rounds of ginger (should look roughly like a coin) into a cup and pour boiling water over. Let sit a couple/three min and enjoy. You can add honey, lemon, tea (put a tea bag in iwth the ginger) or anything else that sounds good. I leave the ginger in my cup and add more water if I want more tea or it gets too strong. The coin size pieces can be used for several cups of tea, at least for me.
If you are a big iced tea drinker at home, try putting a few pieces of ginger into the tea when you start it? It makes a very refreshing iced tea when used with either regular or herbal tea. Even thank you likes it, and he doesn't eat anything new/wild/foreign to him, lol.
One last thing, gas. Sometimes if you have gerd you also have problems with gas. If you do, or you eat a lot of cruciferous veggies (broccoli, cauliflower, etc...) or you eat sweet potato (the musical fruit because it makes you toot, according to my mother), you will have gas. Beano may help if you can tolerate it. GasX is also helpful. Walmart sells two bottles of 72 gelcaps for around $6-7 and it can be a big help. If you eat much dairy, give lactaid a try. I won't buy the milk. It is crazy expensive. I get the walmart version of the tablets that is called Ultra Dairy Digestive Enzyme. You chew one with the first bite of food, or two if it is a big serving, and it can make a HUGE difference. Even if milk was not a problem before, humans lose the ability to make the enzyme as we age, so it may be a problem you are just not aware of yet. A trial of a few days generally will give you some idea of if you have a need fort this. Be sure to try it with a glass of milk, serving of instant pudding, etc... and not just with yogurt, cheese, etc.... Sometimes the process to create yogurt, cheese, etc... can actually help it b digested, so trying it with uncooked dairy products like milk or instant pudding can give a truer picture. Or so I have been told repeatedly.
I hope something of this helps.
