If you are leaving the 10 pin constantly, you aren't actually in the pocket if you want to really get down to it. As hank said, you're probably "coming in behind the head pin" and hitting a little too far right on the headpin for the angle you are entering from. Is the 6 pin wrapping around the 10 pin (a "ringing 10"? If so, that's the problem. Or is the 6 pin falling dead in the gutter (a "flat 10")? If that's the case, you are hitting weak.
To help counter ringing 10 pins, try softening your ball speed a hair (moving forward on the approach can help this), or using a little more surface on your bowling ball, or try a totally different line. You will need to be hitting with a little different angle, and you need to hit more of the front part of the head pin (though not a lot). Your ball is going too far and hooking too late in general when you're leaving ringing 10 pins.
To help counter flat 10 pins, you can either move your feet and target right (you'll have to gauge how much each should move by your oil pattern you're on) to get the ball to hook into the flush pocket better instead of hitting it light with a weak angle. Alternatively, you can try to use light pocket hits to your advantage and kick pins around and trip the 7 pin a lot. Watch a video of Norm Duke throwing it pretty straight from the gutter to see what I mean by that.
Really pay attention to the angle and position of the ball when it hits the 1-3 pocket. Watch other bowlers and see what generates strikes, and what leaves 10 pins, 7 pins, 4 pins, and 8-10/5-7 splits.
