All in the mind. I think you should work on that aspect first before resorting putting stuff on your bellend. You only have one and it can't be replaced. Just sayin.
Truth. I have always had problems "holding back", even with my fiance of 8 years. It is completely in the mind and over time you find ways to make it work. There are websites with pages of suggestions as to what to think about while holding back. An understanding woman who won't judge you if you have an 'Oops' is key. If you're all worried about impressing her, you'll pop as soon as you touch her.
If you absolutely need a crutch, opioids are well known for allowing a person to be in complete control of their orgasm, but as you know they are addictive, especially in this sense. It's a one-two punch in this case because not only are they already addictive, but now that addiction spills over to thinking you need them to have sex and will avoid sex if you don't have any due to the fear of busting early. No good! Also, I find with conventional opiates, it's often hard to come at all. You could try kratom, it's far less addicting and still works for desensitizing, but feeling the need for it when the coitus opportunity arrives is definitely still there, I've suffered from this. Nowadays I'm definitely finding myself in much better control.
Don't do silly things like "picture your grandma naked!" because that will ruin it for you. One thing I do, I closely observe artwork on my bedroom walls if I feel I need to reel myself in. I find this works, and the over-sensitive part only lasts a couple minutes until you get your groove on, then it's easy to control it. Think in actual physics terms, you're causing friction on your skin which after a while will desensitize the mildly-irritated skin, thus allowing more control.