Thanks for your query.You have not stated your age.Have you done your ultrasound
scanning? Do you have enlarged prostate?What was the average urine flow per second ? As your urine flow is weak these questions need need to be answered. Your Dr has prescribed Rapilif 8 mg.to improve your urine flow This drug relaxes the smooth muscles in Bladder Neck and Prostatic Urethra
.and improves the urine flow.During normal ejaculation the sphincter of the urethra is opened and bladder neck is closed preventing semen from going in to bladder But due to this drug which relaxes the bladder neck which remains open resulting into flow of semen going into the bladder but enters into the bladder. That is the reason it does not come out during ejaculation.This will become normal once you stop taking this drug.You can consult Urologist
to change the drug.