Hi,
Welcome to HCM.
How frequently do you masturbate?.
If you are a regular mastubator, then the semen may become thin and less in quantity.
Reducing the frequency should help.
You will need to get your
semen analysis done and if the
sperm count is low, you will need a Colour Doppler Study to exclude
varicocele.
If frequency is not the cause for thinning, then best is to consult an
Urologist who will have to examine you and do investigations to find out the cause and treat accordingly.