It sounds like you are really straining to go fast, which feels right but is all wrong. YOu can only get really fast when you learn to relax as much as possible, as long as you don't let your hand fall off the guitar. Then, when you are relaxed, play slow, and build from there. I am slowly getting speed in my playing, and it only started once I learnt to relax and start slow. By accepting that it isn't going to happen overnight, you actually ge tthere a lot faster than if you try to get to vai speed immediately.