But this isn't about his sensitivity... I mean if it were you could start calling him all sorts of degrading terms and that would really make
him a lot more sensitive.
What we are discussing is his
penis.
Yes I used the word Penis.
And there are a lot of sites that discuss sensitivity of the
Penis.
As others have suggested (which I will just put out there as bluntly as I can) your partner has spanked the monkey too often, choked the chicken too hard, buffed the banana to peel it, beat the weasel with too much vigor.... oh I got a million of these.
I suspect that he hasn't had many sexual partners other than Mother Thumb and her four daughters and has gotten a tight grip - if not a hard, calloused palm to bring to bear on the meat of the matter.
What he is going to have to do is lay off, and allow time to take over.
One thing he can do is to have you moisturize the willy for him. Mind your job is to gently, say with two fingers only, rub on skin lotion. Might help if he orders you with '
It puts the lotion on the skin before it gets the hose again'. Get that whole Master/Slave kink involved (never know you to might actually enjoy it)
If he absolutely must charm the snake, he may want to get one of those
fleshlights, which are far, far gentler on the skin. But now that he has you I don't see why you can't assist him in the ritual of dancing around the maypole.
The other aspect here is performance anxiety. Those partners of mine who required a wee bit of extra patience and labor to achieve orgasm always worried I was working to hard - it thus became my job to get them to understand that I was actually enjoying the extended time and having my skills tested...
This becomes a circle of self defeating, the more you think you are not being appreciated for your staying power, the more work it takes to get off... and yeah, after an hour the jaw starts locking, the throat is a bit raw and you just want to spit it out and call it quits for the evening.... So to short circuit that you got to get him excited and believing that you are really, really into what you are doing for him and most happy if it never ends.... YOUR enjoyment leads to his enjoyment. So moan, and groan and do the complete opposite of good table manners and do talk with your mouth full - or try.
Mind one of the things I have discovered about guys who cannot get off without a lot of work, is that being deep throated tends to set them all afire... So work on expanding your throat and get over that gag reflex.
If he can relax into it, and know that this is not a race, he may get more excited by the whole process and reach orgasm earlier. If you can convince him that this is the best sex you ever had, he will feel it is as well.
Sex mostly takes place between the ears. Thus sounds, smells, sites and notions lend great power to the whole sex thing.