Miguel, howlong did your frog not eat? He can't be a week old if your feeding him crickets, pacmans at that stage still have tails and live in water, or did you mean you've owned him for one week?
Pacmans can go a while without food, don't force feed emediately. Give the frog some time to adjust, if you've owned him for a week, and allready force fed him, chances are your frog is under ALOT of stress.