From what I know, feats are granted during levels 3/6/9/12/15/18 ... being 6th level, I think you got the Tower Shield Proficiency for your path by default. You'll be able to get another feat at 9th level (Improved Critical: Slashing Weapons for your current path), but to get THF, you will need to 'get off' the Mighty Protector path.
If you do decide to get THF, you'll find yourself not using the Tower Shield Proficiency feat much ... since you cannot use a shield and a two-handed weapon at the same time. However, if you are still getting a feel of the game, THF really is the way to go. Going TWF really needs a more experienced player, plus it needs to be planned and done from level 1.
Good news is that you can swap a feat thru Fred, your friendly neighborhood Feat-swapping Mind Flayer (
http://ddowiki.com/index.php?title=Fred& ). So you actually don't have to wait until 9th level to get your THF feat, if you decide to swap it with something. You can (if you haven't already) get a free feat swapping token from Lockania (
http://ddowiki.com/page/Hall_of_the_Mark ) after finishing the Hall of the Mark quest at the Marketplace.
You can then swap out your Tower Shield feat for Two Handed Fighting feat. However, you might want to consider getting the Power Attack feat instead and just use a two-handed weapon with Power Attack on. +10 to damage in exchange for a -5 to hit ... which is what I did at your level. Hope that helps!