Eating out and stomach pain

Ok! So I have always had a diet which involves making my own food. Lately it's been about 2-3 times a week I buy something to eat for lunch /dinner and everytime
My stomach gets so tight and bloated and I have a hard time the next couple days. I know the logic answer to this is don't eat out but I am wondering if anyone has experience with this and can give me insights as to why. I've tried various selections from a sandwich to Chinese food and everything does this to me unless its prepared at home.
Can my stomach just not handle the what it's prepared since I generally eat at home?

Thoughts?! TIA