car lost power?

1 week ago i got in the car after work and when i tried to start it , it didn`t fire up it just clicked loads, so i bumped it and it ran fine , got home turned it off , restarted it and it fired up fine.......

then today after work i got in it it started fine but after about 50 meters it suddenly lost power put my foot on the clutch and the revs went back up and started driving normaly and then 200 meters down the road it just stopped no power then within 30 minutes i couldn`t put the windows up when the head lights were on , severe loss of battery power