Practice makes perfect.
Be confident, but not forceful with your gear changes.
Match the revs to the gear you're selecting, then quickly but smoothly release the clutch.
Learn where the catch point is, it does take a while.
If what you say is true and you're being pushed back into the seat (sudden acceleration) when you change gears you might be leaving your foot on the throttle a little bit when you've got the clutch in.
But again, practice, just find a nice loop of quiet road and cruise around until you get the hang of it!
Good luck.