Yogurt is good protein. Not the sugary, flavored stuff. Ideally you would make your own, but second best would be a good quality unflavored, unsweetened Greek yogurt. If you can't stand it plain, drizzle on a spoonful of *good* honey or maple syrup. It's an acquired taste for some peeps, but I like it plain if homemade.
You should eat what agrees with you. A few days or weeks without meat won't harm you. It's high quality protein, but strong food your digestive system may not be up to processing right now. Eat what you can tolerate. Stay away from sugar and anything that you find unappealing.
Is this digestive upset a new thing? Are you sick, or is it a chronic problem?