When a guy doesn’t ejaculate during sex, especially when he’s been going at it for a while, he may be experiencing “retrograde ejaculation,” a condition where the bladder’s sphincter doesn’t close off properly during emission. So the semen ends up getting emptied into his bladder. This “dry come” situation can be due to physical reasons, like diabetes, hypertension or prostate or urethral surgery. Men can also experience it during Tantric sex.
In making sure that your body’s response is not a symptom of a larger problem, be sure to consult with your physician about the situation. S/he should evaluate you for the impact of any medications (or other drugs/alcohol), possible nerve damage, and hormonal factors, amongst other possible organic factors at play. Be sure to discuss any potential psychological or relationship issues that could be affecting your response, like stress, anxiety, sex guilt, fears (e.g., getting an STD), orientation issues, past traumatic events, and a host of emotional anxieties, as these can make it hard for a guy to sexually perform. If your doctor can rule out any physical problems at play, you may want to consult with a sex counselor or therapist on any personal issues involved. No matter what, don’t let “finishing” define your performance or the quality of the sex you’re having. “Cumming” shouldn’t be the goal and the only mark of a great sexual experience because it is also about the intimacy it creates you’re your partner and the enjoyment of the “ride!”
Thank you for your question and good luck!