My boyfriend cant have intercourse with me

[Jennie31]

Hi, me and my partner have been together for more than a year and a half now, and still have not been able to have sexual intercourse.
He gets excited about having sex, but then when it really comes to having it, his penis goes down. This has been happening since the first time we tryed having sex. He (26) claims this is happening as a result of the stress in his life "at the moment" and stress that he should make a good impression on me...and acted as if he were surprised this happened. Although I felt that he has had this problem even we met, since he was pretty much confortable with it. The person that I am, I didnt make any fuss over it, since I can understand it does happen to men. But the bigger problem is now, that he doesnt even try for us to have intercourse.  Another big problem is that we live in different countries and we see each other about two to three times a year, which makes it harder to work on the problem. Every time we see each other, he gets stressed and feels under pressure that something must happen. Again, the person that I am, I have told him many times that sex doesnt matter so much, what is important is our great love for eachother. I feel as if he has gotten extremely confortable with that, and doesnt try anymore. Our relationship has gotten to the point where, when i go to visit him in his country he shows me around town, I sleep at some friend's of mine house, since he still lives with his parents, we go out, he droppes me off at home and thats it. The most we do is kiss...we dont even talk about our problem anymore...
So I really dont know what to do about this, we really do love each other and I would really like to help him overcome this problem. Im sure that he doesnt see this as a "problem" and that he wouldnt go and talk to a doctor about this problem. What could it be with him? could really stress for school be it? Since he is attracted to me, and he does love me, im more than sure that im not the problem, that it is a psychological issue. How do I help him overcome it? How do I make him see a doctor or take medicine to help it? It is really ruining our relationship, since we are repressing the passion between us.