I'm going to show my girlfriend pictures of my exes who were way better looking than her
Why would you do that to her?
I don't have any fears of getting dumped. I want to see her reaction.
You shouldn't make your partner feel bad about themselves. You need to treat her better and show her that you love her.
Doing that is my way of showing that I love her
You need to find different methods to show your love. The way you are going about it seems to be quite the opposite of showing love. Try getting her flowers instead.