When Gluten Attacks

I ate at this restaurant twice before with no problem. Chicken breast sandwich, plain, gluten free bun, tomato, nothing else. This time I ordered it with pickles. Could the pickles have made me sick? Was there some cross contamination with them? Was the grill contaminated this time and not last time? Or did I get such a slight bit on contamination in the past I just put it up to something else?
This time;
Day 1 - Headache within minutes of eating.
Next day big tummy problems and lots of bathroom visits. Pain in abdomen all day. Like a stomach virus where the pain kind of floats around and bites hard. Hardly eat anything all day. Had to lay down.  Drank a lot of water
Day 3 -  Still have stomach pain. Especially bad after eating. Ate some pineapple for breakfast, avocado & hummus on Udi's English muffin. A lot of pain after eating. Skipped dinner. Ginger tea. Water.
Day 4 - Pain gone, very tired. Starving!

And that's my gluten reaction. I wish I could know how the contamination happened. Was this a lot of gluten that hit me so hard or just a bit of cross contamination?  There's only one way to find out and I'm not going there!

Gluten free since 2003.

How does gluten hit you?