My boyfriend is at my house and we have had sex before and we have been doing stuff for around 5 months now, but for some reason my vagina is tight and he can’t get his fingers in?

Can someone tell me why this is happening and how to help? We do not have lube.

UPDATE: We ended up just leaving it because we think that I was too tired so therefore was not fully in the mood.

We tried again the next day though on more sleep and it was amazing.