i got a serious problem building chips in poker tourneys , i wll reach middle stage every time with lack of chips i.e blinds will be 1000/500 my stack will be 3000-6000.
i will wait for monster cards like AK,Asuited etc .
but i am not able to double it up .
Given your figures, you only have 3 to 6 big blinds left at that point. Using ten as being considered by many as "short stacked", you are
still short stacked, even after you double up to 6k or 12k, with blinds at 1k! Plus, just prior to level change if you are at Big blind = 1,000, then a 25,000 stack is 25 big blinds. When the level changes, the big blind is now @ 1500 and the same 25,000 stack is then only 16 big blinds;
you lost 9 big blinds in reserve in only two hands once the level changed! In your extreme short stack case, this is your end. Even the ante makes a big dent in your stack.
This also means the reason you cannot double up is that;
A) with so few chips, you are just not a threat to
anyone other than another short stack. So big stacks will call you with a much wider range just trying to knock you out. Plus it is hard to get heads up this short, so they will just "play over your head" 3 or more at a time, again, just to get rid of you. More than HU is a greater risk that your hand will not make it. And even if you merely double up from 6 to 12 big blinds and wait for that monster to re visit you, you are right back in the same situation.
B) waiting only for big cards makes you a easy bullet to dodge as after
you sit there and fold 10-20 hands in a row the whole table knows you have big cards when you do finally play a hand. It's all you play, obviously! So while they might call a preflop raise from you, they simply fold when an ace/big card hits the flop and they cannot beat it. So you cannot get value from your
hands when they just fold. And they know you are
bluffing when big cards are not on the flop. Hard to
bluff something other than a big card hand when that is all you play.
Survival is key in an MTT but I think you are going way to far with it and playing scared, IMHO. You must be willing to play other than AK and continue to play good hands along the way, or become an "open book"; everyone knows your range and plays around that. Just shutting down and waiting might get you a few spots higher in the pays, but will almost never see you ever actually win an MTT.