There currently seem to be lots of for, and pro, circumcision lobbyists jumping on threads like this at the moment. (Come on guys, back off and confine your argument to relevant threads.) I want to reassure the OP that, from my experience as someone who was circumcised at age 30 (I'm now 56), circumcision doesn't make a significant difference to sensitivity. Certainly not significant enough to cause the OPs problem.
There are several factors that cause you to come before you want to. For example, if you are having sex with someone new, you are stimulated by the novelty, and eager to impress. That means you're both excited and anxious, both of which makes you come quickly.
If you are in any way insecure in your relationship with the person you are having sex with you will be feeling eager to please, and the anxiety will make you come quickly.
If you are having self doubts (about your attractiveness, cock size, etc.) you will feel anxious and that will make you come quickly.
If you are not having sex frequently you will be using lots of muscles during sex that are not conditioned to the activity. They get tired quickly. And you are hard wired to ejaculate before you are exhausted, so you'll come quickly.
For the same reason as above, you might come quickly if you are very tired/fatigued because you've been working hard and not getting enough sleep.
The above are just 5 (of many) factors that impact on your sexual performance. You have to understand that you are not a machine. You can not expect yourself to perform the same way every time you have sex. Who you are with, and how relaxed you feel play the biggest part in your sexual response (not whether you're circumcised, or wearing a condom, or whatever).
Having a tendency to come easily is a very normal and healthy. The thing to work on now is your fitness and your mental state. Ask yourself how secure you feel. Communicate with your partner. Remember that most partners feel flattered if you are excited enough to come quickly, and that after a short recovery rest you should be able to go back to having sex and you will last longer second time round.
Best of luck.
Warm wishes
Riven