Okay - so you don't have a fever, and you have been checked out. I would still encourage you to look over articles to help you rule out possible emergency situations, like appendicitis and gall bladder issues, as they can crop up at any time.
And am I understanding right that the stomach symptoms rotate/trade places with head symptoms??
Going on the assumption that your organs are okay, and just dealing with these infections, are you taking magnesium? It could be the muscles in the intestines are cramping. I get this all too much. Magnesium can be helpful with muscle cramps, but you don't want to get the magnesium oxide, as that will mainly pull water into the lower bowel to help with constipation issues. Here is a good article to help you find what will work for you - I use magnesium orotate:
/www.globalhealingcenter.com/natural-health/types-of-magnesium/ Try putting a heating pad over the area - heat will help relax the muscles.