Might try Triple Washing your Butter, same as outlined here but you put the butter back into pot with water and cook/cool two more times...

This is a liquid to liquid transfer and will remove 70% of the Med Taste and other nasties that might be the cause of your problems...
ZZTops Reviewed by ZZTops on . Butter gave me a headache. The butter was made with Shiva Shanti - 1oz. I followed the method described in this forum. After eating it, a mild headache occurred and stomach became nauseous. Neither lasted long but it seems every time it was consumed the same symptoms occur. The Shiva was not fresh, it had been frozen in vaccum sealed jars for almost a year (Shiva is not my favorite, it was kept for cooking). What would cause these symptoms? Rating: 5