How many meeples should I have according to the expansions that I'm currently using?
The list of expansions that add pieces for each player are as follows:

Base game


7 meeples, plus one for scoring.


Inns &amp; Cathedrals


Adds the Big Meeple.


Traders &amp; Builders


Adds the Builder and the Pig.


Abbey &amp; Mayor


Adds the Mayor, the Barn, and the Wagon.


Bridges, Castles, and Bazaars


Adds 2-3 bridges and 2-3 castles, depending on the number of players.


The Phantom


Adds the Phantom.


Of the new pieces, only the Big Meeple, Mayor, Wagon, and Phantom are truly meeples.  The rest of them change the rules but can't be placed on their own.  In the games you listed, you're right, you should have 9 meeples.