I also experienced the same thing. After taking hydros started having anxiey about 2 hours after taking a pill. Also when I tried tapering one pill a day I had major anxiety. I am 24 days clean and still have more anxiety than I would like but glad to say it is better. I would say if you never had anxiety and are still on the pills you have built a tolerance to them and the anxiety is your body telling you you need more. That's just my opinion. Good luck
Peace
It could be that you have built up tolerance and are feeling withdrawl. I tried to taper off Opiates and the anxiety was worse than I ever thought was possible. Is it worse in the morning when you first wake up? That's when you will likely have the least amount in your system and when withdrawl/tolerance anxiety would be the worst. Whatever the reason for it, 123456m is right . If you try to think it away the anxiety will get worse. Fear of the anxiety attack is what makes it worse. Try to accept it and let it pass through you. This worked for me, but it took practice. Getting off the pills is the only way to end the cycle if it's related to them.
It may be but may not be. You can have a aniexty disorder also that is not related to the pills. But one thing at a time. If you keep trying to think your way through your aniexty will get higher. Get clean off the pills and then see how you feel.
Peace