How can i get stronger to generate more bat speed?

i am going to be playing highschool baseball with a -3 bat. im 4' 10'' and 85lbs. I swing the bat so slow i can barely get the ball out of the infield. Its not my mechanics because i have worked on my mechanics for years. With lighter bats in the league i used to play in i hit over .500 avg. So what workouts/exercises can i do to help me generate more bat speed? Also How much faster could i swing if i do what you say?