Instead of varying up your bet why not consider varying whether you continue a bet onto the turn or not? I play a very similar style and found that even your style can be predictable. You will find that the more solid players will call more often on ur flop knowing that they can steal the turn since you will check ur missed turns opening a steal opportunity to them.

I would make 2 suggestions:

1. vary up ur bluffs and make a 2nd continuation bet on the turn to force them to realize that even if u miss they are goign to face 2 big bets

2. If u have check/folded several turns that u missed and been bet into, then check/raise a big hand on the turn to extract more money

Hope those help to keep your play more unpredictable