Getting my Boyfriend to orgasm

We’ve been seeing each other for a couple of months and the sex is amazing but he doesn’t cum every time. I asked him about it and he says that it takes him a really long time to get there even when he masterbates. He says to not worry about it because he really enjoys the sex and loves seeing me orgasm. I mange to orgasm every time with him which is amazing because he’s the first person to get me there. I just feel guilty for not being able to get him there. Any advice or tips to try out?