I can totally relate to that. One of my ex's actually broke up with me because he couldn't get me off. It took me years to figure out how to orgasm with someone else, and it's still really hard. My body knows exactly what it wants, where it wants, and when and how it wants it, and if anything gets messed up at all I'm just not going to orgasm. I was lucky enough to find a partner who didn't get too upset about it and was willing to learn what to do. Figure out exactly what you are doing when you get off yourself, and make him watch you do it or explain it in great detail. This requires a level of comfort that wasn't easy for me to achieve, but hopefully you can get there faster than I did. Tell him to resist the impulse to do what he thinks will work, or to improvise, or to do what worked on someone else. He needs to do EXACTLY what you tell him to!! You can work on changing it up later, but first you have to let your body get used to someone else doing what you usually do yourself.