Thank you for your reply!!! What you said exactly echoes what my mother has told me - binging my own dish.
I am a Chinese, but now living in the USA. I thought American people might think I am odd/weird to bring my own food when we are invited for dinner. Maybe I just have to explain to them that I have Crohn's.
Another thought comes to me is that if I find nothing I can eat over their dinner table, I can slip out to eat at a nearby fast food chain. I can eat McDonald fried chicken sandwich without any problem.