There are too many things that could be hindering you, it's pretty much impossible to advise. Even if we could see your playing in a video, it's not the same as being able to correct you as you're playing. Get with a teacher ASAP (Bill Bachman has a great series of videos and does Skype lessons -- look him up).
That said, there are some things to think about as you try to build speed. First, resist the urge to tense up. Bounce the stick off the head; don't just "hit the drum faster". Second, the faster you play, the more you'll need to rely on your fingers to bounce the stick, rather your than wrists, so it's important that your pinky fingers not stick out, and that the fulcrum (pivot point) is between the pad of your thumb and the first crease of your index finger. Finally, to develop your fingers, it will help to work them out individually. Check out Technique Patterns by Gary Chaffee to see what I mean.
But if you want to just take the advice of some dude on the internet...
Find the first page of Stick Control (search for an image of it), and practice that page on a practice pad with the metronome set first to 80, then 100, then 120, and then 140. Play each exercise 20 times every day (about 20 minutes of practice). Bounce those sticks, keep the right and left stick "heights" even, and play each note with equal volume (no accenting). If you're not considerably faster after a couple weeks of that...