Porn Addiction Help!!!

Hello everyone.I'm a 14 years old boy who addicted to porn video. Actually I have a crush on a girl, she fascinating. Unfortunately,we are not very close. I always watch the porn videos and imagine have sex with her. But after I watch that,I feel self-abased. I don’t want to watch that anymore but I can’t control myself.I want to change myself from now on but I don’t know how to start. Could everyone give me some suggestion(s) to fix this problem?thx a lot!(Poor English, please forgive me.)