Before you say your fresh water tank is bulging full... drain your gray water. If your pump runs and runs and runs - the fresh water is EMPTY. I don't care what the sensors say. Unless you have a sewer line hooked up and your gray tank drain valve open, that's where all your fresh water went.
BTW I have a 2005 Safari 25 FB with a 30 gallon fresh water tank - three longish showers and wash dishes twice and it's sucking empty... and the gray tank is full. I DO move water to the black tank by plugging the shower drain, and using a pump to put the water left in the pan into the toilet which has a dowel rod holding the drain slightly ajar.
Betcha money it's your gray that is full. Your owner's manual will show you the locations of your tanks. BTW some of the smaller units have a combined gray/black tank, so hook up the slinky and feed it into a sewer cleanout before you pop that drain valve!
Best of luck Paula
Today is a gift, that's why they call it the present.