if it's especially apparent after orgasm,it's also due to the histamine reaction orgasm causes:
Research has shown that histamine is released as part of the human orgasm from mast cells in the genitals, and the histamine release has been connected to the sex flush among women. If this response is lacking while a woman also has trouble achieving orgasm, this may be a sign of histapenia. In such cases, a doctor may prescribe diet supplements with folic acid and niacin (which used in conjunction can increase blood histamine levels and histamine release
also note too,taking anti-histamines such as for a cold will fuck with your ability to cum