You didn't give a lot of details, your age? Are you having any sort of symptoms at any other time?
Any nerve tingling? Perhaps you should consider consulting a neurologist?
Also, check into the lab tests at enterolab.com. Food intolerances have some very odd and delayed symptoms, including forms of extreme fatigue.
This syndrome is called POIS (Post Orgasmic Illness Syndrome).
I often (almost always) have the same experience. I avoid ejaculating altogether because of this. I usually feel drawn and tired and bit down the next morning. It started when I was about 34? and i am not 44.
I *** about twice a year now. It is not not worth it. I have never heard of "Post Orgasmic Illness Syndrome" that B_Jim posted about.
Does anyone know anything about it?
There's a lot of discussion of this on the Naked Scientist Forum and here: http://sites.google.com/site/poiswebsite/
There seems to be a theory that it is autoimmune in nature. There's some interest in a link between POIS and celiac/gluten intolerance. Some reports of casein intolerance. However, some people seem to feel that removing all grains and eating low in carb is helpful. The Paleo diet might be an option.