Hi Blanche :^) Gluten is a protein found in some grains. Someone with Celiac Disease, has a severe reaction to gluten and it will cause trouble in their gut, and systemically because they don't absorb the nutrients from their foods. So, they can become malnourished, vitamin/mineral deficient and weakened immune system, even though they are eating regularly.
It sucks because gluten is in soooo many things! Even soy sauce and salad dressings aren't safe. There are more and more gluten free products being offered, so there is some good news. And some stores (like Trader Joes) carry a wide selection of gluten free products. I do well with rice, oats, and most corn products... if they aren't mixed with wheat. Celiac.org has lots of info on gluten and how to recognize it in labeling (for instance: "modified food starch") . Generally, it's wise to stay away from already prepared foods.
Probiotics: A healthy human gut has a mix of living organisms in it, that when in balance, helps it to maintain health and proper function. This mix can become unbalanced when conditions like celiacs, stomach flu, antibiotics, irritable bowel, and perhaps severe stress occur. A course of probiotics helps to restore the natural balance (the gut flora). Yogurt has some probiotics, especially a good greek yogurt. But it doesn't have enough to put things right if the gut is really imbalanced, so I get probiotics at a health store, drug store, or off the internet. They can be expensive, but after a couple weeks you don't need to keep taking them... just eat some yogurt a couple times a week. Also, cook with real garlic and onion, helps keep the gut in good health.
One other thing I found that I could not tolerate was soda pop. It would temporarily help to sip on a diet soda, but cause way more pain in the long run.
Like I said earlier, you will need to experiment to come up with what works for you. Good luck and keep checking in with your progress!