MacBook Pro runs for only one or two seconds

Hey guys!

I had some problems with the monitor, one fan and the dvdrw, so I bought them from ifixitm followed the guides. And everything worked! But I realized my camera cable was broken as well. So I didn't put the screws yet! I am trying to get the money to buy the cable as well.

Anyways, in the meantime I used the mac and everything was just fine for more than 2-3 weeks(being without the screws, it's like a desktop pc, but that's ok)

Everything was fine and dandy until this morning, when it refused to start. If I press the power button, it starts and shuts down in less than a second. If I keep the power button pushed, it starts (I hear the dvdrw squicking, the fans rolling) but after a few seconds, the frontal led (on the push button to open the lid) starts blinking fast, and everything shuts down (fans stop, the hard drive makes a specific "out-of-power-sound")

I am guessing the led blinking fast is a sign and somebody might know what it means!

Is it a short-circuit?

Thank you, all for any advice that might get me to fix this problem

ygr

PS: I only kept the battery and it's the same thing. The same with only keeping the power cable and taking out the battery.