wont start

i have replaced the battery and the alternator about a month ago and the headlights would still flicker while i drove it and now idrove it to work the other morning and it drained the battery completely dead and would not start got a jump and drove it home during the day put a new battery in it and did the same thing but this time when i drove it home it missed all the way home and did not have the power it usually had so could it b something more than the alternator