Yes, I've had this problem, and I'm not a great fan of too many teeth... You don't say how old/experienced the girls were who gave you the bjs (and you mightn't know for sure anyway what their experience has been), but that could be a factor. I doubt it's anything you're doing wrong, if that's one thing's that worrying you.
Positioning is a big factor too, and you might need to experiment because what works for one woman might not be so good for another. Therefore, you both need to be prepared to try different things: some women are happy to do this, others not so much. Sometimes it helps if she is on her back with her neck extended; to do this you need to find something for her to lie on that's the right height (or you need to have good knees!). But the key is trying different things and see what works.
If she can't take too much of you, try some other things - e.g. she sucks your head or licks the frenulum while playing with your balls, and so on.
Anyway, just some thoughts.