How do I get my african clawed spotted frog to eat?

I have only had him a week. I have tried blood worms, frog bites, reptile food, caught bugs. Sometimes he puts the food in his mouth and he spits it back out. He just sits there, and swims occasionally. Any help will be appreciated. I am afraid he will starve if he doesn’t eat.
Is it true that frogs can go on a fast and not eat for a while?
If so how long?

If you just got him then he is getting used to his surroundings. Just put food in twice a day and leave it overnight with a verity of foods. He will eventually eat, and then you can also see what he likes by what he eats and does not!