There's a few details you left out which
would help - like - has this always
happened at this "time" or is this only
recent? Your age? Are you having
intercourse with someone other than your
usual partner?
Possible causes could be:
guilt (going behind a parents back,
cheating on partner, or even just the fact
that you're getting pleasure from sex -
unlikely if this is recent rather than a
long term issue);
age & hormonal changes could cause
migraines (which is what you seem to be
describing);
if this started when you first started sex
& orgasms then again I think of
hormonal issues which often cause women to
have migraines.
Religion? Some religions teach that women
should not enjoy sex so therefore if you
enjoy it you may feel guilt & so
"punish" yourself with a migraine.
Just some thoughts based on the very
little information you gave.
