Hi, I'd like to help you with your question.
There are a number of possibilities that could be causing your boyfriend's sexual issues.
One, he could have a hypoactive sexual desire disorder. This means that he could be interested in sex and women but when confronted by sex, his lack of sexual drive surfaces. This condition affects many young men and tends to be undiagnosed due to the embarrassment and reluctance to deal with the issue. This is treated medically and the success rate is very high.
Two, he could have issues with control and feel that sexuality, which is highly emotional, feels out of control for him. And as a result, he represses his sexual thoughts and actions. This is treated through therapy and also has a good success rate.
Three, he could have had a bad sexual experience in the past and feel fearful over his ability to perform sexually.
Four, he could be over stressed and feel anxious, depressed or just too tired. Since society often sees the male as a desiring sex all the time, he may feel embarrassed or ashamed of how he feels. Most men do not like to seem vulnerable so it prevents them from dealing with any emotional issue.
In any case, he should be seen by his doctor to clear any possible medical problem. If he is cleared, then the issue is most likely psychological. He should talk to a therapist to find out why he feels the way he does and to help him recover. To find a therapist, he can talk to his doctor for a referral or he can search on line at http://therapists.psychologytoday.com/rms/ (search in the lower right corner for Canada).
There are also resources to help you at home as well. Educating yourselves about why this might be happening and how to resolve it helps. Here are some to get you started:
Why Men Stop Having Sex: Men, the Phenomenon of Sexless Relationships, and What You Can Do About It by Bob Berkowitz and Susan Yager-Berkowitz
Rekindling Desire: A Step by Step Program to Help Low-Sex and No-Sex Marriages by Barry W. McCarthy and Emily J. McCarthy
You can find these books on Amazon.com or your local library may have them for you.
I hope this has helped you,