Since you have steatorrhea and malabsorption, and problems digesting carbohydrates and fats, have the doctors checked your pancreas? I had this problem 5 years ago. I had CAT Scans and Ultrasounds which came out normal. This was sooo frustrating because I knew something was wrong. But my symptoms persisted and I lost weight. At 85 lbs. I had to find a doctor that was willing to do an ERCP. I was ecstatic when they finally did this test and diagnosed me with pancreatic divisum. I have had surgery for this which opened up my pancreatic ducts. Also I take pancreatic enzymes which help to digest proteins, fats and carbohydrates. No matter what the diagnoses is, it is better to put a name to your illness so that you can better understand how to treat it. Do not give up. Get a second and third opinion until you find a doctor that is willing to get to the bottom of your problem. There is hope for you problem!
Please look into Candida yeast. In the abscence of your normal bacterial flora due to long periods on antibiotics, candida yeast that is naturally present in low levels can flourish and cause all types of problems in the upper and lower GI tract. Many people who suffer from this are not immuno supresses. Carbohydrate consumption is something that causes a flare as well because it is essentially food for the yeast. Even though you have been taking probiotics, beneficial bacteria flora establishment can be a long and difficult process, especially in the case of candida proliferation. Lots of info on the wed. Check it out.
If you 've got villous atrophy and fat malabsorption, have you considered the possibility of celiac disease or problems with the pancreas? Have you been tested for either?