My boyfriend has delayed ejaculation. I was wondering what I could do to help and what this means for us as a couple? Also in the future are there ways of me getting pregnant if he still has this?

Hi. I am a 24-year old male. I have done sex with girl friends 4 times until now. But the problem is that even after, say, 10-15 minutes of continuous intercourse I am not able to ejaculate. I get exhausted and I have to leave it because the girl also gets exhausted. When I masturbate by lying upside down and stroking the bed, which is my usual way I get ejaculation.
Is this some kind of disease ? Is there any problem with me ?