What Causes Difficulty In Ejaculation During Intercourse?

I have a boyfriend age 57 who has a large & engorged penis, have been with him for more than 6 years. But I find it hard for him to ejaculate, even in the midst of sex. He says he s not taking any enhancements. it s getting difficult for me due to the fact that i have endure physical activity for long periods of time, to the point of me being in pain/raw. what seen to be the problem?