I get lower stomach pain when eating at restaurants. Is it the oil in the food? I tend to go bm after returning home.

Could be +. Based on your sx and timing with relation to eating dinner, it is very likely related to something your ingesting. Possibilities include too much oil/fried foods, certain food sensitivity, see if you can determine what foods precipitate the problem. The most important part of the story, is eating out at restaurant. Over 95% of problems (infections, etc) related to eating occur out, not in, home.