Cash Game Help Needed

The game I find myself playing a lot of lately is .50/$1 NLHE. I try my best to maintain a tight/aggressive image, but I'm not afraid to mix it up from time to time. What I've really been working on lately is trying to read the other players. This has resulted in winning more pots when I'm fairly sure I didn't have the best hand.

The problem I'm running into now, at least I think it's the problem, is that I'm always playing against the same people. And I think they're starting to catch on to any moves I make. Several of these players have told me that they have a horrible time getting a good read on me. I try very hard to always go through the same motions and act the same way when I have a hand or not. What's happening now though is these same players have decided to start calling me down when they've caught any peice of the flop. In a way this is a good thing, but it is forcing me to play a more straight-forward form of poker. As a result, my winning sessions haven't been as nice as they've been in the past. In fact, over my last four sessions I've only managed to break even.

So how do you approach a game in which you've played a lot against most of the other players and it seems that they have figured you out?