Hard to do with that build
As most other posters have stated, you've got a rogue who really isn't built for melee and you want to get into melee. I've played melee-combat rogues before and they're plenty of fun, but they're also hard to play and very dangerous (both to enemies and to you).
For starters, one thing you need to realize is that you cannot melee like a fighter. If you aren't dealing sneak attack damage, you better be certain you're fighting something that isn't meant to be a major melee threat. Your primary goals should be hitting spellcasters and support characters.
The Two-Weapon route is obviously tempting for the extra attack, but it isn't always the best bet. Generally, unless you invest some levels in fighter or ranger, you won't have the BAB and feats necessary to use TWF successfully. Try playing around with a spiked chain or even a two-handed weapon (or a rapier and a shield) to see if TWF is really what you're looking for.
Assuming it is, I'd try to pump up your dex (to help your attack rating with weapon finesse, to open up feat trees, and to give you much-needed AC and initiative boosts) and drop the alertness feat. If you can't raise your dex up to 18, I'd try to get 14 strength, you'll save yourself a feat, you'll open up more possible weapon combinations, and you'll get a minor but worthwhile damage boost to your attacks. Improved Initiative, TWF, and (at level 3) weapon focus would be a good starting feat trio. You'll need 14 con as a minimum. Try dropping your charisma, you'll probably end up as more of a scout / recon / assassian type, so trying to split yourself between a social rogue and a combat rogue is just going to give you huge headaches.
At low levels you should be pretty powerful, mostly because you'll have a good combination of dex and armor to keep you out of major trouble. You'll start to run into problems around the mid-levels, when enemy BAB gets dangerously high and your AC stays dangerously low. If you grab a few levels of fighter, you should invest in dodge and two-weapon defense, the extra +2 AC can be a lifesaver, especially since it will stack with everything else you're doing. Generally, you can murder any spellcaster provided they don't get a will-based spell on you first (thank goodness clerics and wizards have miserable spot scores), and you can hold your own against any general combatant aside from tank fighters. Heavily armored fighters are essentially your biggest weakness, they deal enough damage to put you in the ground and have a high AC that flanking doesn't help to counteract. Make sure you keep a ranged weapon handy, your decent dex scores and light-armor mobility let you make a great archer in a pinch.
Fighter / Rogues are my favorite class to play, and when used correctly they're one of the most lethal class combinations on the battlefield. Just rememeber, keep repeating to yourself: "I am not a front-line fighter."