HJ listen, this is bound to attract the pervs, but ignore them and stay with me here.
1. He can sometimes get hard and get in in. Good start.
2. Let him go on top. It's easier for him to keep hard because (i) he can control how it is feeling, and (ii) simple gravity helps ... if his stiffy is facing downwards, the blood stays in it more easily.
Okay, now ...
IF he loses it ... options
3. Make him feel that you are still turned on (which you may be). Say "Don't stop" and push his face down between your legs. If he makes you c u m, he will feel better about it. Then you say "Now, how about you?"
4. How do you finish him off? I guess we all know the answer to that. And the best way is to prop your head up on a pillow, let him straddle your chest, and take him in your mouth. You both get to c u m, and he will feel that the exercise was a success. Next time you make love, he will know that even if he 'loses it', all will not be lost.
And that ... will help him not to lose it.
Now, the other option ...
5. As soon as he loses it, do the propping up and taking him in your mouth thing. Either ...
(i) he will get hard againg, and he goes back in. Or
(ii) let him finish off, and then do you.
The end result is that you have a successful bonk every time. He knows that you are both going to c u m no matter what. That will relax him more that anything.
JHT - bit graphic i know, but this will work babes (and ignore the pervs who will no doubt try to sabotage the rest of this thread) Go for it girl !