Lasting only a few minutes is from inexperience in my experience. I'm also a one shot in an hour kind of guy.
Very early in my sexual escapades as a teenager, I had a few experiences where I came very early and seemingly on a hair trigger. I was upset, my partner was amused/unsatisfied and needles to say the experience was terrible.
Hasn't happened in many years, i think more experience cured the problem.
Somebody else mentioned it already, but pacing yourself during sex makes a huge difference. If coming too early, it's it because coming in hot guns blazing?