Need advice on skipping a dentist appointment

my mom made a dentist appointment for me, it is today at 2:30. I try to keep a 3 day rule for needing to leave the house. this way I have time to prepare and make a plan on how to tackle the day (im talking shower the day before, have time to say no I cant go work up the courage to either go or face my parents and say I cant). I was told about this appointment today, at about 9 am. I have been in a severe episode for about a week now, I have been neglecting to feed myself if the food wasn't prepared for me, ive been spending all the day laying in my room with the lights off only getting up to use the bathroom and grab whatever I can to stop my hunger shakes. I absolutely can NOT go to this appointment, but I am also on the edge of a panic attack because im terrified of telling them I will not go. Im mostly just venting in an attempt to calm myself down, but if you have advice or also want to vent, that's welcomed.