One cannot get power attack with a str of 10.
The thing I see is that true strike is only good if your attack actually deals damage. This applies to all attacks basically, but so far your character is focused with feats and spells into making the hit but what you have done is put an enormous amount of energy into hitting but you still only do 1d6 each attack.
So the question is how to deal more damage. There are a few options here: More attacks, more criticals, bonus damage.
The increase number of attacks will come with level, or you could spend two feats when you get them on multiple attacks. This is a long termsolution however and by the time you get more attacks you will still be doing minimal damage for your level.
I would personally use your feats on improved critical (when it is available) and combat casting (as soon as possible). Then grab the keen spell as quick as you can.
That leaves the bonus damage. There are three options as I see it here: poison, magic weapons and sneak attacks. Poison is a character choice but you might consider it. Magic weapons you want are things like flaming blades so keep an eye out for short swords that burst into flames or are cold to the touch, etc. But really, I think your best bet is Rogue. Go for the sneak attack. Use your rogue skills on bluff to get easier hits and multiple sneak attacks. You have the charisma to make an effective diplomatic type rogue. Keep the rogue, fighter and sorceror levels all about equal, with the rogue and sorceror always advancing before the fighter class. At level 20 you will not be as effective as others, but if you choose your sorceror spells and rogue skills wisely, you should have some useful talents.