I'm a sixty year old male (should be obvious)and I have been seeing what you describe since the early 1990's. Looking at a blank - bright field shows all floaters including what you mention.
Mentioned this to a doctor friend and they thought I was mistaken. Having seen male semen in film clips - it is hard to mistake it for anything else. I understand that some men after a vasectomy can see this. Maybe the semen being absorbed and showing up elsewhere in the body? I have not had a vasectomy, so who knows?