I am not circumcised and I can go for 2 to 3 hours or more. My dick is very sensitive. I can stay on the edge of orgasm for a very long time. Everything feels just too damn good. Just getting over the edge is a problem. I can not count the times I have been told to "please stop". That kills it for me and I can not even finish masturbating. There is some kind of disconnect between my cock and what triggers the orgasm.
Like you, I'm uncut, super sensitive, and routinely go for ages. I've never heard "please stop" (usually because I get super conscious about how long I'm taking and switch what we're doing frequently to keep my anxiety down), but when I hear "are you close?" it sends me right back to the beginning because A) I'm probably not, and B) it gives me performance anxiety. Luckily, I'm in an LTR with someone who is used to my dick's foibles and is quite skilled at working with them and working around them.
So I guess I would say, OP, that sensitivity isn't necessarily the issue. I agree with the posters above in advising you to get used to a less intense touch; kung-fu grip is definitely no good for sensitivity. I'm not familiar with what vaginal sex feels like, but I'm sure it and death-grip are leagues apart
Also, please remember that "less intense" doesn't have to mean slower or less pleasurable. In fact, lighter and slower doesn't have to mean less pleasurable, either. Frankly, I get closer faster when things go lighter, slower, and longer.
Also, I'd suggest trying more foreplay. Ultimately, it's not your penis, but your brain and nervous system that decide when you're ready for orgasm. So getting yourself horny is every bit as important as what your dick is doing.
Good luck finding out what's good for you. If you ask me, that's half the fun.