Say,
I received your reply in a private message. There a several fundamental actions you can take to increase your average. I am basing my feedback on the errors I most commonly see in bowlers that I have coached.
First of all, are you finished in a balanced position when you slide to the foul line? If not, the #1 consideration is a poor ball fit. Assuming you had the ball fit by a reputable
Pro Shop operator, balance problems can be cause by squeezing the ball or the lack of a weight shift at the finish (moving the arm opposite to the ball-side away from the body and and the non-sliding foot to the side opposite of the ball.) Finshing balanced at the foul line is critical to consistently hitting your target and controlling ball speed.
Let's start with this aspect and continue the dialogue.
Rich