relax relax relax. Getting all worried about it is the exact opposite of what you want to do. Performance anxiety is something you can really only conquer by letting go of all that tension. Stop thinking "oh my god I have to please her!" or "I can't let her down" or "stay up stay up stay up" ... all of that will just cause mr. winky to head south as it were.
I'd suggest trying this:
set up a time where you both can just touch each other. have a little fun. caress. explore. all with this understand...
orgasm is not a priority
just have fun. do that a few times (finish with oral/touching if you like). once you can learn to be relaxed in a nice sensual environment then you'll be able to put it on and have some fun. Though, don't be surprised if you have to put it on then take it off again cause it's not cooperating... just start over. no hurry.
Good luck.
