carbonation problems

my last few brews have been consistantly lacking carbonation, I haven't changed much of my process, except for the fact that I now hold my racking cane above the cake at the bottom of the fermenter to avoid pulling up as much sediment as possible. Is this taking too much yeast out to properly carb the beer? After 2 weeks there isn't even a hint of fizz. I've tried adding more malt to fix this, adding as much as and extra half cup for a 5 gallon batch. Can anyone point me in the right direction

What kind of brew? Big OG?

How long has this beer been fermenting before bottling? The yeast could be tired.

Are you using malt as your primer? Dextrose general takes about 3 weeks to carbonate but malt a week or two more.

I am using malt as my primer, and the og is not really that big somewhere in the 1047 to 1060 range, another question to go with this will an infection change the way the beer conditions?