Car won't start, nothing but a click

I've had this problem on and off for the last month, but now it just won't start up at all, I believe it is the starter relay clicking when I turn the key and that's it. I thought it was a battery problem at first, because I was having problems with my terminals, they were stripped, loose, wore out, and all I'd have to do is wiggle the positive terminal around, turn the key and it would fire up. Now since I've replaced the positive terminal, all I get is the click sound, I've checked the wires to make sure they are secure and all, so that should be good. I've checked my battery and that is at a solid 12.5 - 12.6. I've checked the voltage running to the connection of the starter relay even and I've got good voltage coming through there as well.