Based on the information you have provided you are correct in assuming that there may be a psychological component to your boyfriend's difficulties. You have established that he can achieve an erection and reach orgasm through other means of stimulation. His difficulties during intercourse with you may be related to the differences in stimulation he experiences during penetration or may reflect some emotional issues (for example, anxiety) he experiences during intercourse.
Honest communication with him about your wish to improve this aspect of your sex life is essential. Doing this without blaming will be very important. You may want to identify a therapist familiar with addressing sexual performance issues and then volunteer to make an appt. for the two of you. If he is initially reluctant to go it may be helpful for you to see the therapist yourself for some guidance in this matter.
Rick Wirtz