You don’t get excited by pushing the right button. What counts is what happens in your head. If sex fills your thoughts you will notice this in your body. There are even women who can climax by using only fantasy. So make sure you are turned on in your mind when you masturbate. How to do this?
When you caress yourself you can close your eyes and pretend it’s the hand of a good looking guy or girl.
You can read an erotic story before you start masturbating or while you are stroking yourself.
You can look at erotic pictures.
You can think back of a exciting experience you had or of an exciting movie you have seen.
When you fantasize, as if you are looking at a movie, you should put yourself in the position of the 'actor(s)' and try to feel their excitement. The more you are able to connect with the sexual feelings of the 'actors' in your fantasy the more excited you will become by fantasizing.