Started noticing clear and very little ejaculant when I orgasm also a few years ago while in service over seas saw our medic ref. pain in the groin he said I that my testicles or testicle had rotated the pain went away and now my problem is slowly coming back along with the little or no semen.
Degree understand your concerns went through your details. I suggest you not to worry much. The quantity and viscosity of semen depends on so many things like water intake during the day, physical wellness, strength, stress etc. These factor do contribute largely. You started noticing now but the fact exists always.  Chat Doctor. Hope this answers your query. Available for further clarifications. Good luck.