How long should "normal" intercourse last?
It's hard to say, much depends on the subjectivity of the two partners. What is too short for one person can be absolutely normal for someone else. In some cases, however, ejaculation occurs even before the penis is introduced into the vagina or only a few seconds after. The fact is that when you experience premature ejaculation, there may be insecurities and fears affecting your emotions and relationships.
What can you do about it? See an andrologist who can rule out any organic cause (inflammatory or neurological) and set up proper treatment. Even when one can not find a specific cause, in some cases, it is possible to introduce specific pharmacological therapy that improves the symptoms.