I think your problem is probably that your re-raises define your hand too strongly, and you're starting to grasp the importance of mixing it up against opponents who don't suck. If you're only re-raising big pairs and AK, a decent player will pretty much know exactly what you have after he sees what you do on the flop and the turn. This is a bad thing.

So sometimes you should just call with AK, but sometimes re-raise it, and sometimes re-raise suited connectors and small pairs as well. That way you can take down a lot of pots with air on ace-high or king-high flops when your opponent folds to your obvious AK. By the same token, once they know that you don't have AK too often here, you might start getting more action on an ace-high flop when you do happen to have AK in a re-raised pot.