John, I'm wondering if you're overdrawing the bow as your back muscles develop and losing the straight line that should be from the arrow point to your elbow. Overdrawing the bow with back tension can lead to the bow arm torquing to the left at the shot on a right hander. It's very common with our wheelie friends when they go to a back tension release. I always shoot best when I relax a little as I anchor. Also check your anchor point. When you're using your back hard it's very tempting to lengthen your draw length an inch or 2 to pick up the speed that comes with it. If you aren't careful it'll mess up your form/accuracy, especially when you shoot in uneven terrain (or out of a tree stand). I have never seen where drawing an arrow too far (or too short) with good form did anything but raise or lower the impact point. Inside 15 yards it has very little effect. Beyond 25 yards or so it has a much larger effect.
There is a product called the clickity click (from 3Rivers) that works with traditional bows, but it most certainly isn't primitive. Unless you shoot off your knuckle so you could feel the back of the broadhead, or an index mark on the arrow, I don't know how you'd check draw length on a primitive bow.
Good luck,
George