Hello,
I have gone through your query and understand your concern.
I suspect it is due to either
retrograde ejaculation or swollen
prostate.
Because usually semen drops out immediately after
masturbation and left over semen is usually dropped some time in inner wear due to gravity.
1. Retrograde ejaculation
In this, While masturbating, some semen may enters into
urinary tract instead of urethra. This may stay there and pass out as thick semen on urination of next time.
2. swollen Prostate- if your prostate is swollen, then more seminal fluids are secreted and mixed with urine and pass out as thick viscous liquid.
Swollen prostate is usually due to infection in young age.
Thus rule out any infection or retrograde ejaculation by examining urine and physical examination.
If there is a retrograde ejaculation, you may need surgery to get corrected.
In case if you have
prostatitis, then you should need antibiotics to clear infection.
Hope this helps.
Please write back for further queries.
Wishing you good health.