Since you were able to fall asleep it is not the same panic attack. it may be about the same situation but panic attacks don't last all day. At any point in the day where you are able to return to a calm state such as napping the attack has stopped. Im guessing what is going on is that throughout the day the upset stomach comes back along with thoughts about the situation which is triggering the shakey, I cant breath feelings. Now that you know you were able to relax and go to sleep think about what you did to reach that level of relaxation and sleep. Do those things now only not to the point of falling asleep. Since they worked once in order for you to fall asleep they WILL work again. All you need to do now is step back and look at what you did to get you there and you will no longer be in panic over this one situation. if for example it was breathing then everytime you feel panicky remind yourself to think about being in your bed doing the breathing. and the panic attack will stop.