Presumably, performing oral ahead of time would make him last longer, since he will have already ejaculated. However, it really just depends on the guy, and this is something he needs to work on himself. Since he was a virgin when you first started having sex, and it's only been a few times, he has a lot to learn about mastering self-control when it comes to ejaculation.

I agree with Brandon; masturbation would be a good way for him to learn. He may already masturbate, but he may not have done it with the practice of self-control in mind. In time, with you and perhaps by himself, he will get the hang of it. It just takes practice and experience.