Why don't you tell them you are allergic to wheat/gluten?
Maybe you aren't, but for all intensive purposes you may as well could be. If food is making you feel this shitty, listen to your body, you shouldn't be eating it. I find it odd that the program you are in has a rule that you cannot make requests of food in your host home. What about the people who are legitimately allergic to stuff? Like the people who go into respiratory trauma from eating pistachios?
I am sure the Spanish family can understand your food allergies, if not that, smell the evidence of stomach discomfort from the bathroom.
Stumbled into Primal due to food allergies, and subsequent elimination of non-primal foods.
Start Gluten-Free/Soy-Free: December 2012; start weight 158lbs, Ladies size 6
Start Primal: March 2013, start weight 150lbs, Ladies size 6
Current: 132lbs, Ladies size 2
26lbs lost since cutting the crap.