Tiffy, please call the airline and tell them it is an ESA. You might print up a tag to hang on it's container (that fits under the seat in front of you)... put it in fine print, but put the truth. They don't have to allow it, but most want to be able to. If you that IS your carry-on, and you are quiet and polite when speaking to them, being honest, odds are they will let it fly in the cabin.

Don't be afraid to ask them to ask the pilot if they can make an exception, should they insist no emotional support animals in cabin. If you tell them about your panic disorder, and how the animal calms you, they probably will want one for every passenger!

You might be required to pay a $50 fee for the ESA to fly in cabin under the seat. IDK GOOD WISHES ON THIS FLIGHT!