My boyfriend had a bit of a problem..?

keeping it up when we were having ... he could get hard and start to enter, but then lost it... But he didn't have any problem if I was performing oral. I was a virgin the first time we tried, he is not, I'm almost 30 and he is 40. We've been together for almost a year. He blamed the anticipation of it all and stage fright, but it happened 3 different times. What can I do to help him out?