New racket altered my game?

ive just been out and bought a new tennis racket because mine was slightly too short for me. the new racket ive bought is a HEAD liquidmeatal S6, my old one was just a dunlop no make cheap one. the new racket is about 3 inches taller overall (about 1 inch for the grip and 2 inches for the head) and ive worked out that where i would be hitting the ball on the old racket is on the shock reducer and way too low on the new racket. because of this i am having troubles with returning the ball and serving. i had a fairly low but confident serve before, now i have to throw the ball higher and i am unconfident in hitting it at that height, and on my returns i am hitting the ball too low on the racket and it ends up being less powerful than needed or goes off in a different direction entirely, can anybody help or give me tips to improve with my new racket?