Need Advice about ED

I'm 28 years old and I have been having trouble with ED ever since I have become sexually active. When the time comes for me to be intimate I get an overwhelming nervous feeling that prevents me from performing. I just feel that I will come up short some how and because of this my erections are hard to get and don't last. I can get an erection easily when I'm not in a situation where I am expected to perform. I guess when I'm under no pressure I'm able to fully relax. I’m certain that my problem is psychological but I just don't know what to do about it. I feel to embarrassed to speak about it with anyone because I am an attractive and well off guy who people generally assume has a lot of success with women. I recently met a woman who I do find attractive and we click very well. When the time came that she wanted to be intimate the nervous feelings just overwhelmed me and it wasn’t the sexually experience she was expecting. Now she feels that I'm not actually attracted to her and is losing interest in me. I don't want this to ruin what looks to be a good relationship and I don't want to this problem to cause me to keep ruining relationships.

What should I do?