Boyfriend can’t cum

I recently took my boyfriends virginity a few weeks ago and we’ve had sex three times since, I’ve had lots of sexual experience I know what I’m doing but all three times he hasn’t been able to cum, he actually had to go and finish himself off in the bathroom after... I asked him if it was me and he said that everything was fantastic but for some reason he just can’t get off from sex only from himself. Heeellppppp