Addictive to masturbation. Please help.

I am 26 yr old, unmarried. My problem is that all the time I have this thought that I have to masturbate. While I watching movie or when I am studying or while I m travelling, in between I get this thought that I should masturbate. If I am at home and if it's even slight possibility that I can masturbate, I will. Now as I am on 2 months leave for my exams, many a times I end up doing upto 4 times a day. Sometimes even when I don't have erection I Will watch or think something and bring the erection and do masturbate. I guess because of which I don't get proper erection. I penis is never fully erect. I can't even hold on to my erection. I m unable to perform intercourse, which is very depressing. I don't have any habit of smoking or alcohol. How can I get rid of this. Please help.