Limp dick help😭😭

Elena💓

Okay so me and my bf have been together for about 4 months were about to do it and his dick wouldn’t get hard what does this mean ? Is it because he’s nervous,cheating ,tired ? Or already jacked off or something but idk what it could be we have a good sex life so I just thought it was a little weird .caught me off guard he’s 22 btw