Well, since you said I shouldn't tell you how to live your life, I'm not sure you even want my advice, but I guess I'll give it to you anyway.

You might be able to get a script for Tussionex if you tell your doctor that you've had a cough for a while and it gets worse at night so you're having trouble sleeping. Over the counter stuff (Delsym, Robitussin and Mucinex) isn't helping at all. You had a prescription for some little yellow cough pills that didn't do anything when you tried them, either (those are called Tessalon or benzonatate if they suggest it - I don't think most people would remember the generic name, which is what would be on the bottle, so "it started with a B" is probably good if they ask what the bottle said). You could've easily gotten those from urgent care or had an old prescription in your medicine cabinet.

They may be willing to give you a bottle of codeine cough syrup (that they almost always give a full bottle of). Tell them that you think codeine gives you a headache because you had one after you took the prescription your dentist gave you.

That's about the best you can do. It's going to depend on your doctor, but you might be shit out of luck if you're expecting a full bottle.

I'm not sure how they'll feel about prescribing either codeine or hydro syrup along with your Percocet.

As for the T3 script you got, they know which doctor prescribed them and it was a tiny amount, so they probably knew it was from a dentist. They don't usually care too much when it's something like that.