It is Normal for him not to eat for a couple of days. make sure your crickets are the appropriate size for him. the space between his eyes is about the size of cricket you want.
Have a water source and plenty of Fresh salad finely chopped. Avoid Spinach especially during Growth. it interferes with the absorbtion of Calcium.
Make sure you remove any un eaten crickets. They will also cause him to stress they will bite and also eat his feces and you do not want your dragon eating the crickets after they have done that.
Another good way to make sure he stays hydrated is to soak him in warm water in a container for several minutes. They absorb water through their vent if you slowly pour water into the container the sound and splashing will also encourage him to drink. They are kinda dumb :-D
Good Luck with him!