How to quit exhibitionism and frotteurism?

Hello doctor,

Recently, I started exhibitionism. I had not known what I was doing until I read on the internet that it is a psychiatric disorder. I also came to know that it is an abnormal behavior. My first abnormal behavior before I started exhibitionism was frotteurism and masturbation, which began when I was 17 years old. I feel that this is not right, and I always vow myself not to engage in this weird practice. But, I find myself doing it whenever I get the chance. I want to quit because I feel ashamed of it. I get worried thinking that I never going to quit these habits. Currently, my girlfriend does not know about this, and I am not planning to tell her, but I will tell her years after I have quit. I feel it is the right thing to do because telling her might jeopardize our relationship. I would very much appreciate it if you could help.