He's super protective of you, and doesn't want to bother you with anything. He hates showing any sort of emotion, so talking to you about this was really difficult. He just wants to make things better for himself. he was afraid you'd hate him if he told you he was struggling. 

He's determined to do everything by himself. He doesn't like asking for help. He prefers to try and do things alone. He  things he's protecting you. He tries to brush it off with jokes. He loves you. 