After years and years of masturbation, it can take time to get used to the different sensations of 'blow jobs and stuff' and find them enough to orgasm. You'll probably find he doesn't come via intercourse the first few times if you do have sex with him.
Accept that he's enjoying it, feel free to ask for instructions (most women don't masturbate a penis as firmly or as quickly as its owner does), do whatever it takes to get him close to coming (including having him masturbate until he's close), and it will come - sorry! - in time.