What does it mean when he comes to quick but that never happen before? *GUYS* please help?

okay this boy and i have done it countless times but we have not done anything since feb. But today we did and he lasted 5 minutes. But most of the time he lasts at least to 40 minutes. What is wrong? with me or with him? is he losing interest? or was i good thats why he came so quickly? please hlp! *GUYS*