Is it normal not being able to give oral for a long time?

So last night I tried to give my husband oral as I know he likes it but... I'll 9nly do it if he has recently showered, so he did but I find i can only hold him in my mouth for a few seconds like 10 max and then I have to pull back. If I go too far I do gag alot, I've never gotten him to cum from a bj or from stroking him to completion... is this normal or am I kind of abnormal on this one? Today is a good day to learn...