I'm so sorry you're going through a double-whammy of flu and anxiety - absolutely no fun!
First off, since you've got flu and diarrhea, you need to take steps to prevent dehydration. Make sure you're drinking fluids - water, tea, broth, or gatorade/powerade cut in 1/2 with water. Ginger ale might help with your nausea and get some sugar into you, too.
Keep in mind that anxiety can feed off what is happening in the body. For example, there is a huge nerve system that runs down the center of the body and connects with the digestive system. If the digestive system starts to experience distress, that can manifest itself into anxiety. I've been down that road, and it's no fun.
Dehydration and lack of nutrition can also contribute to anxiety as your body burns off the fuel it's stored up and realizes it's not enough to help fight an illness battle. Since you're fighting the flu, your nutrition and electrolytes are probably all kinds of out of whack.
The paper bag thing was a good choice - an imbalance of oxygen and CO2 in our systems can cause anxiety, as well.
If you're still miserable after 3 days of flu, I'd follow up with a medical professional. In the meantime, make sure you're drinking plenty of fluids, and eating what you can. The BRAT diet is good for diarrhea (bananas, rice, applesauce, toast). Alternate advil and tylenol to manage fever and body aches. Hot showers, keeping warm and comfortable, and concentrating on good breathing techniques will help manage the anxiety.
Put some dvd's in, listen to some music, and just be kind and gentle with yourself. Your body's fighting a lot - hang in there! Hope you feel better soon!
I have panic disorder and I know exactly how you feel. I know it sounds very cliché but just try and relax. maybe try drinking some warm milk, eating lettuce or even taking a warm shower. don't pay much mind to anything else. I hope you feel better.