The main symptom of premature ejaculation is not being able to delay ejaculation for more than three minutes after penetration. But it might occur in all sexual situations, even during masturbation. Premature ejaculation can be classified as: 
Lifelong. Lifelong premature ejaculation occurs all or nearly all the time beginning with the first sexual encounter.
Acquired. Acquired premature ejaculation develops after having previous sexual experiences without problems with ejaculation.
 Many people feel that they have symptoms of premature ejaculation, but the symptoms don't meet the criteria for a diagnosis. It's typical to experience early ejaculation at times.