Thisby

You asked what it was exactly, well a friend and I were discussing this very question the other day. Here's some of what I dug up:

"Ejaculation in the early stages of excitement"... doesn't sound like you, "or soon after the insertion of the penis into the vagina"... that sounds more like it.

"Premature ejaculation occurs prior to when a man wishes it or too quickly during intercourse to satisfy his partner." (hahaha, who wrote that one? )

Or "Ejaculation with little stimulation."

Other sources said normal ejaculation should occur within 3 to 5 minutes of continuous thrusting. So at 2 to 3 minutes, you're only a little short, especially since you've said you can prolong it by going slowly.

Anyway, there's no test for it, and I don't own a penis, so I couldn't really say. If your main concern is that you don't seem to last long enough to give your gf a vaginal orgasm, statistics put the percentage of women who are able to orgasm through penetration alone (no clitoral stimulation) from anywhere as low as 10% up to 30%, depending on the source. If she's one of the majority who don't, you could be one of those guys who lasts an hour and you'll still never get her there. Unless she's unhappy that intercourse isn't as long as she'd like, I wouldn't be placing so much emphasis on it.