Had the same problem myself. Recently I took the peep sight off my string and use a kisser button. With my sight, I removed the bubble level that came on it and went to only 1 pin. This seems to help me concentrate more on my target with less other STUFF to worry about.
Since I did this my groups are better and I can hold on target longer before I release. Dont know if this would work for you but it did for me.