This depends on several factors:
- Your age.
- What sort of stimulation you are receiving.
- How long it is since you last had an orgasm.
- Whether you worry about this or not.
It is normal to come after receiving 1-2 minutes of direct ongoing stimulation. This might be through intercourse of some sort, oral sex or manual stimulation. Generally speaking if you are 20 you can expect to ejaculate more quickly than when you are 50, so this average covers a lot of variation including when you have last ejaculated.
The important question is - do you and your partner find the sex satisfying? Remember you do not need an erection to bring your partner to orgasm or to enjoy being sexual together. Also, the less frequently you have any sexual activity to orgasm, the more quickly you are likely to reach orgasm.
If controlling when you come is your concern it is useful to learn to identify the 'point of no return', the moment just before you orgasm. With practice you can pause at this point and not rush to orgasm.
Enjoying whole-body sensuality and tuning into and enjoying your body will allow you to better understand the different stages of arousal. If you are a reasonably confident person and your relationship is sound then all you may need is a self help book such as Bernie Zilbergeld's New Male Sexuality.
A sex therapist can help you learn to control ejaculation but do remember that sex is far more than just a performance. It could be that the most important thing you can do is stop putting pressure on yourself, to stop worrying, relax and enjoy the closeness.