If for some reason talking is difficult, perhaps you would want to write to him how you feel.
Try to find out what is causing this difficulty in you (fear of misunderstanding, judgment, rejection, ridicule, etc) and try to work on that issue within your self. He would not be able to know how you feel unless you express it.
When you are ready to share your feelings, start with what had happened to make you feel a certain way and keep it straight forward. Whatever you do, do not place a responsibility on him for causing those feelings or the difficulty in expressing your feelings.
Men are more factual. Let him know what you want him to know and if you have an idea of how to change a certain situation, offer a solution to him.