Unfortunately, stomach viruses such as yours can leave your stomach really messed up. It does sound like you have IBS type symptoms as an end result and especially if you are having panic attacks too. This is due to the mind/gut link with certain chemicals being released from the brain that also have an effect on the smooth muscle linking of the gut.
Have you had a stool sample taken lately to test for bacteria/parasites to see if you have any infection still present? If not, you should think about this, but then you need to be evaluated for the IBS problems to see what is going on.
The fact that you have panic attacks and gas are all quite indicative of IBS and quite a few people seem to get left with IBS following severe cases of stomach viruses or bacterial stomach infection.
Good luck