I'm pretty sure that what you've described is normal. My boyfriend was a virgin the first time we had sex, and although be didn't have any trouble coming at all during penetrative intercourse, I couldn't get him to come when I gave him a blow job. I thought it might have something to do with my technique, but I think it was more that it was a sensation he simply wasn't used to.

I don't have any trouble sucking him off now. Takes only a few minutes.