My shots are waaayy off now! Help!!?

Hi! I used to be an excellent shooter, but now pretty much all of my shots are airballs or clanking off the rim...I just started weight training, and also I used a different ball, it feels slightly heavier and bigger, if that matters...but am i going through a shooting slump?? does the weights affect my shot? how can I adapt to it or overcome it?? thanks!! :D