My wife told me last week that having sex with me presented problems for her and always has. It stunned me into emotional unconsciousness. Her problems: I'm too large in girth, I last too long, and I stay hard after.
I always thought I was average as far as sexual things are concerned. None of my partners said otherwise. I make a point of a lot of foreplay and lube, natural or purchased. Now, I don't know what to do.
My feeling is that you need a partner that can appreciate you for you. This sounds like a problem that can not be fixed. Physically or otherwise.
I will suggest you reassure her to be more relaxed during love-making. Most importantly both of you should try and spend more time during foreplay and this will greatly help.