Car is acting as if my 2 week old battery is now totally dead.

Wouldnt start this morning. Only working light was
ignition circle on steering column. Checked and no
lights or anything had been left on. After trying to
crank it, no sound or clicking. Turning key to 'on'
position would do nothing until closing the door,
then all the symbols on dash lit up and it would
beep. Only happened twice. Jumped off and
cranked. While driving to work, the headlights
dimmed when I pulled a window button.

Part store said alternator was fine, but it didnt get
checked inside, only with the handheld while the
car was cranked. Check engine light has been on
and they got the code P1135.