One thing that maybe a factor here , as maybe/probably/possibly (covered myself there  :-? ) for others aswell that are having some difficulty is tension in your hand.If the hand is tense then the fingers will be also i think that if there is tension in the thumb you will grip the neck to tight, therefore making clean smooth changes difficult to say the least.If you need a lot of tension to hold the strings down then you might want to look at your action but if you are playing an electric there should not be any tension at all.Its easy to say i know &  it happens to us all when doing something new we natuarally tense up but with time a bit more practice - well a lot more actually - & it will come to you.You'll be helping new members to BBG with their woes about the "dreaded" B7 chord in no time at all Alexander Â
LP
...just don't start me on C7 ok Â