Ejaculation Issues

Anybody have issues with their significant other not being able to ejaculate? It has never been a problem for my husband and I before, but the past three times we've had sex he can't seem to finish. Nothing has changed for either of us personally for this to now be an issue. He said it feels like he's close but can't seem to get there. It leaves me feeling like I'm not pleasuring him and both of us frustrated. Any ideas on how to fix this problem?