I think you'd better speak to the person giving the bj, I'd wager that the problem lies there!
I would bet good money on this.
H0neymustard, there's a planet full of uncut guys who absolutely fucking love oral. It has nothing to do with that. In fact, in my totally un-scientific experience and according to my somewhat-slutty (and I say that with the greatest love) circle of friends, uncut guys seem to enjoy oral more and have less difficulty coming from it.
No, by far the number one culprit for bad sex - bad head, bad handies, bad anal, bad anything - is in the technique. The only way to change that is through communication.
People have to learn how to have sex well, and that extends to oral. There are a few lucky guys who can practice on themselves, but the rest of the world has to learn through experimentation with others (and even those of us who can blow ourselves learn pretty quickly that other guys like it differently).
So you have a sensitive dick. I'm the same way - and I'm uncut. That means that the ladies (in my case, the gents) can't just clamp down with their lips and treat it like a popsicle. They have to tease it, go light with their lips, light with their tongues, and go slow, slow, slow. At least, that's how it has to start. Guys with sensitive dicks have to be more communicative about what they like when they get head. It's a bit of a burden, but the pay-off comes (pun intended) when someone gets good at it. Oral goes from being a bit ouch-inducing to the kind of toe-curling, slow-burning, shouting-to-the-rafters pleasure that porn stars do such a bad job of imitating.
Since (according to the side-bar under your avatar) you're American, OP, you're also going to have to do some educating about how to handle a foreskin, as that's not standard issue in your country. Luckily, it's a nice lead-in to communicating about taking it slow and using a lighter touch, as you'll have to let the ladies know it's not as simple as yanking the skin back and using as much suction as possible - which, frankly, is a small blessing for the one giving head. As much fun as it can be to bob up and down like a woodpecker for a minute or two, it starts to feel like a chore pretty fast, and it can cause some neck and jaw soreness. Going slower and lighter is more comfortable for the blow-er, too. So in that way, you're in luck.