Make sure your arm is not deadlocked straight or that will happen again. If the bow is set at the right draw length, you shouldn't have to straighten your arm. Otherwise, it sounds like you're a natural at this.
You really should have a bow custom tailored to you... everything down to the arrow length/gr to fit you and the bow. It has to match your draw length and the draw weight of the bow vs the weight of the arrow. You need at least 5gr of arrow for every pound of pull (ex: draw weight of 70lb = 70x5gr = 350 gr arrow including tip)
I've been reading about arrow trajectory and shooting a lot lately. Apparently, if you have a pin set to 20 yds, it should pretty much be dead on at 10 yds, slightly high at 15, then back on at 20 yds. If the second pin is set to 30, all of this changes. Knowing the trajectory of every pin is a must for hunting. This and a range finder. This is why some people love the simplicity of a single or maybe up to 3 pins max. Learn them and learn them well. This is where I am at now in my archery venture.
Good luck this season!