Masterbating

Sarah
Okay, I have a very frustrating problem. I can't really masturbate. I am a virgin but I use tampons. I have tried a number of times to orgasm but I think to much about it then the feeling just dissolves. Does anyone have some tips? Me and my boyfriend flirt and talk and turn each other on but he can get off. I on occasion I actually get a little jealous of him. Please help