Boyfriend can't cum

My boyfriend and I have been dating for two years and having sex for almost that long. I cum easily with him but I can never make him cum. We go for a while, both with penetration and me blowing him, then we need to stop cause I can only take so much. He then finishes himself off and I feel horrible. He used to masturbate a lot but has stopped months ago so we can fix this, but still nothing. Is something wrong with him or me???