Sicilian defense is my trademark now if white plays 1.e4. the problem is that in the end game, i'm being left with only two pawns at the queenside againts white's three.. for after the exchange; 1.e4 c5 2.Nf3 d6 3.d4 cxd4 Nxd4 i have only two pawns in the queenside while black has three and this is always my trouble in the endgame after almost all of the minor pieces are traded away, i cannot stop white from doing a pawn storm at the queenside in endgame since he has more pawn in that part. :(  yes it's true that i have more center pawns after the exchange, but it seems to me that it's harder to mobilize the central pawns to the white's first rank than storming in the flank :(

Use your stronger centre before you reach an end game then. :)

 Actually sicilian engames are generally considered better for black, and it is white who must try to make use of a better center during the middlegame. If the pawn structure stays the same into the endgame then at worst you have a king vs. queen-side majority, which isn't enough to give white a winning edge.

Do you have any of your games with this type of ending available to look at? 

I don't think you understood the picture he painted.  How could white have a stronger centre if his d has been exchanged for a c (one less central pawn)?  Am I missing something, please explain?