Found out it's "his fault" too. Now what?

We just got back from the doctor who says he has early Type 2 Diabetes (still treatable with diet and a pill) and I've heard that can affect fertility in males. He's never had any problems getting an erection, but when he ejaculates (no matter what the circumstances) little or nothing comes out. He says it's been that way ever since he was about 17, soon after a bunch of guys did some serious damage to his testicles with baseball bats. Somewhere around that time was his last prostate exam too, so it's been awhile. We did not have a chance to ask the doctor if it was most likely the Diabetes, some prostate problem that could have developed over 7 years, or the damage done so long ago that has been causing him to not work right and making it so we can't concieve! Does anyone have an educated opinion on this? It's been 2½ years. I have infrequent periods and my doctor said there's not much to be done about me, but what's the next step for him? Is it going to be something unnatural?