This is the experience of "coming" too soon. What “too soon” means depends upon your own feelings. You might come as soon as you think about sexual activity, have sexual contact with another person, before Penetration is gained, just after entry, or before you and your partner have had the chance to enjoy the activity. Any of these may be felt by yourself to be “too soon”. You should take into account your partners’ views too - what might be premature for you might not be for your partners.
This is the opposite of premature Ejaculation, and is when Orgasm and ejaculation takes too long to reach. This can happen occasionally to any man, but when it occurs too frequently then it may be a problem. Remember that you do not need to reach orgasm on every occasion for sexual activity to be fulfilling and pleasant. A sexual partner may also become uncomfortable or experience pain with prolonged thrusting.
Internal Ejaculation is also known as Retrograde ejaculation. This is when the feeling of Orgasm is experienced with sexual activity but no Semen comes out of the Penis . This should not be confused with anejaculation described above where these sensations are not felt.
This can happen for a number of reasons, but mostly it tends to be associated with problems of the Prostate or the seminal vesicles (glands which produce the liquid part of semen).