Stinging pain on ejaculation could be a symptom of infection. If I had this problem, I would want to be sure there were no infection or inflammation of the urinary tract, prostate and/or seminal vesicles.
Is your urine basically clear or cloudy at times? Cranberry helps with a lot of minor infections (yeast and bacterial).
Or it could be a sign the prostate is not contracting normally in ejaculation. In that case, the urine afterward will be a bit cloudy from partially ejaculating into the bladder. A doctor could tell you more about this situation if it's affecting you.
Hi Percy, Not having your age doe's not help, the extra thickness of sperm comes from not ejeculaing to often, If you masturbate on a twice weekly basis you should be OK.
Good Luck