1996 Infiniti J30 dead battery

Two years ago I had a new starter put into my car, along with a new battery. Not until I had my egr valve cleaned did I have issues with my battery not holding a charge or a leak of some sort. One evening after work I found my car dead, and a couple days after that I found my car dead again. I thought it could be the alternator, but that wasn't the problem. I also had my fuses checked, and was told it was probably an electrical problem? If I drive my car everyday I usually don't have a problem, it's when it sets for days is when the battery does not fully charge and a slow leak begins. The only "electrical" problem I have so far is my left hand blinker light goes out occasionally, my cd player stopped working 3-4 years ago, my driver passenger window sticks. Please Help, I can't afford a new car at the moment. Thanks!