I'm having starting problem

[Kaede]

So a month ago, when I left my friend's house, when I tried to start the car, it made the clicking sound. I was thinking, great, my starter is dead. I was able to push start it home, so I yanked out the starter and had it tested at Kragen. They said it was good. So I putted the same starter back in, and the car started perfectly. 3 weeks later, my car won't start again.

Right now, the only way I can start my car is either push start it, or bang on the starter with a wrench till the starter reluctantly starts. Anybody got any ideas what the problem is?