It could be a number of things. If you are shooting you bow at 70 lbs you might need to reduce the draw weight. I'm able toshoot 70 lbs, but I choose to leave it at 62 lbs. I can draw it easier (straight back, start to finish)and smoother ANDI can hold it longer.

Make sure you have the right arrows. If your arrows are over/under spined your groups will be out of whack.

Make sure the bow has been paper tuned and is shooting bullet holes.

Have more than one or two anchor points. If you don't already, use your nose as one of your anchor points. You'll have to move your peep and maybe your pins, but it is worth it! My anchor ponts are: knuckle right behind my earlobe, fletch in the crease between my chin and lower lip, string along the side of my mouth and also across my nose.Four solid anchor points.

From there, work on your form. Shoot with a wrist sling. Let the bowgrip rest in the palm, right across the meat of the thumb. DO NOT grip your bow! Let your thumb and fingers hang loose and relax. The wrist sling is there to catch the bow so you don't have to. If you grip the bow, you'll torque on the shot and throw arrows. Shoot with a slight bend in your elbow. This reduces left/right movement and also reduces stress to the shoulder, plus, you won't whack your arm. Aim small, miss small. In other words, aim at the smallest dot on your target insteard of the general area. Practice drawing on the target, hold the pin over the dot, then let down. This will help you get over the need to let an arrow fly even when the shot is less than perfect. Also, practice holding on the taget a little longer than you normally do. Breath easy and let the pin settle.

Hope this helps.