Hello...there has not been any clear cut cause of
twitch in eye which can explain everything...it has a long list of causes including
stress...when there is no other complain except twitch than mostly stress seems to fit the answer...but as you have mentioned that you have one sided pain of head also ,,,,but further details are not given you better
consult a psychiatrist who can evaluate your headache and stress also and if has anything treatable is there, than you can get relieved by it.