Upset tummy and toilet runs

Is anyone else suffering when you eat a random food that your baby must not like.

I have had 3 bouts of this my whole pregnancy and am now 18 weeks. Where I eat something and it literally does not even hit my tummy before I am sitting on the toilet. I had to keep ducking to the loo while teaching today after lunch. It was horrible and I felt so flat and shaky afterwards. Is this something others have felt???

I have since eaten crackers with vegemite because it sits well on my worn out tummy