My second celi problem, it wont start Options

[NoVa]

I couldnt find a better place to put this so here it is. So 3 weeks ago I jump in my car to go to work and the battery is dead, didnt leave anythign on, nothing. Odd I thought, but I got it jumped, drove to work, and it started up strong since. But yesterday the same thign happened. Got in to go to work, and nothing, not even a hint of trying to turn over. So I got a jump drove to work. Except when I tried to leave work I had nothing again, so I asked one of the guys to jump me. We let those cables stay on for like 10 minutes, and the car never once tried to turn over. Checked the voltage on my batt. 12.4 with car off and no cables. It was getting charged at 13.7 from my buddies car. We were stumped. I wanted to think it was my clutch sensor, but then why would jumping it work in the past. and it cant be my battery because it shoudl start with a jump. Last thing I pulled the cables off, turned on the lights and all the interior stuff, and tried to turn her over to see what would shut off. My clock, gauges and stereo went way dim or off, no sound of hte engine cranking, but the lights stayed bright the entire time! I hope someone can give me a hand with this. Thanks for any help in advance.

Anton