93 Grand Cherokee wont start...

So I bought a new battery a few months ago and just the past few weeks its been dieing. I would charge it completely and then a week later it will be dead again. I had it tested multiple times and the stores say its not the battery or alternator. At first I thought it might have been the new radio I installed, but I removed it for a week and alas, it wont start. I just got done jump starting it and of course it starts right up. Anybody have any ideas what else I can look at?