Overly active, back flipping...

Frogs flipping on their back seems to be a fairly common behavior, but not normal. There is no immediate danger to the frog. It is a sign of stress or some sort of danger, either real or perceived. The best remedy is to leave the frog alone for a while in a quiet place. Eventually this behavior will stop when the frog becomes comfortable. I used to be an amphibian keeper at a zoo and it is quite overwhelming when you see 20 frogs on their back No one seems to know why frogs flip, but it doesn't seem to harm them.

Thanks very much I'll try to give it some peace and quiet. I have been in the middle of packing to move, all the activity could be bothering it I suppose.

As Terry said its a sign of stress. Usually flipping ontheir back is a sign of severe stress as well as jumping into the glass. How long has it been since you changed the substrate?

Do you have 3 sides of the enclosure covered with a nature background or any background?

What exactly are your temps and humidity levels?

Take some pictures of the enclosure and post them so we can get idea of what could be bothering him/her?

What they said
How long had he gone without eating before you tried force-feeding? That should only be as a last resort and, if stress is the problem, it only makes it worse. I personally wouldn't try to force-feed until the frog started to look thin (after peeing, since they can look obese while starving due to holding water).

The waiting before eating can also be a sign of stress. If mine gets spooked by something (you know, something really dangerous, like a door closing down the hall :P) at feeding time, he takes about twice as long to calm down and actually eat. How do you feed? If you can just leave the food in there awhile and not be present, sometimes that helps.