Number one: try the search function as many of these issues have been discussed hundreds of times. This is a large penis site, and most of us have large penises, and to be frank we get a lot of enjoyment that our size brings to our partners. It does make us confident with sex, and this makes sex very satisifying for our partners and ourselves.
And there is a hint to someone who is slightly less than average in length (remembering that women measure penis size in girth - thickness - rather than length). A man who's confident his sexual abilities really turns women on. The other hint is that few women orgasm from intercourse, regardless of size and how long a man lasts. Good oral sex skills are essential. You have a tongue, and if you haven't already, learn how to use it. This will make your partner's sexual encounters extra-special.
Five minutes is not premature ejaculation, and the average duration for intercourse is in the range 5 to 10 minutes. I last closer to 10 than 5, but I don't aim for longer because my girth makes us sore, and my wife is satisified with close to 10 minutes. Remember that my wife and I have sex ever two days or so, and this keeps my arousal to a lower level than someone who doesn't have sex so often. To learn to last longer, use masturabation for practice. Get as close as possible to the point of no return and then ease off, and keep doing that for as long as you can. You can then use this during intercourse; when you get close to orgasm slow down or stop, and then pick it up again. Kegel exercises are essential; do them every day and when you get close to orgasm squeeze your PC muscle and use that to take away your arousal also (look all of these things up with Google). You can use masturbation to practice squeezing your PC muscle to dampen your arousal near orgasm, and then try squeezing your pc muscle during intercourse.
Lack of a full erection may be the result of an underlying medical condition such as high cholesterol or undiagnosed diabetes. Get a full medical check-up, and if that doesn't unearth anything untoward, it's probably in your mind. If so, see a psychologist (I'm a psychologist myself), and explain your problem. They really can help you.
