Relaxation may be important here. If you obsess about orgasm it will never happen because you are stressed and stress releases all sorts of hormones into the blood which are not conducive to orgasm.

Do a search for something called the Yoni (I think thats the right term, I can't remember which is penis and which is vagina) massage. It is a tantric technique for massaging the vagina. It states in the description of how to do it that the purpose is not orgasm but if it happens thats nice. Basically it is a way of touching and manipulating the vagina to relax and give pleasure without the pressure of there needing to be an 'endpoint'.
Set up lots of candles, burn some essential oils, get comfortable and let him get on with it. Use oils (almond oil, but put no essential oils in there) to remove the need for lubrication. You just lie back and enjoy it without feeling that you need to achieve anything.

If you want to pay him back you can do the same for him sometime but make sure you have some 'you' time so you can relax without needing to worry about anything like your performance.

One more thing: If you can orgasm when you are 'alone', i.e. from masturbation then the chances are there is nothing physical wrong with you. So a doctor may not be needed.