Total war mediveal 2?

Is there a tax bug in the game because i'm getting 3864 each turn from taxes but i have 5 towns and i calculated how much i should be getting and its around 8000 why do i get only 3864 gold each turn from taxes its really hard to get both army capable of fighting back and conquering new settlements i had big army enough to continue conquer but the up keep was way too high and i did not survived long i lost 2 towns very quick because of rebellion it was around 13000 army up keep and 3000 wages while i was getting only 12000 from farming,trading,taxes,and the king's money if i was getting 8000 then i would be able to both get good gold and have huge army after i disbanded half of my army the french quickly took back theyr angers town i conquered and took my Caen fortress so is this a bug and how do i fix it or is just the game made that way to make it harder ?