Maybe you both need to calm things down as you go. Sometimes it's tempting to get more and more intense as you go, but if it becomes too much, that's not good. Keep things slow and sensual. Also, he may just not be used to the way it is having actual sex, rather than doing it alone. If he can't get used to ejaculating during sex, maybe if you are the one who uses your hand, that would be a step in the right direction and you won't feel so left out. Just make sure to massage and be gentle. Let him tell you what he likes.