Anon - You've asked some good questions about dealing with two different conditions affecting your digestive system. I bet the combination of the two is pretty stressful.
Let's start with some basics.
Colitis means inflammation of the colon (also known as the large intestine o large bowel) which is the last part of the digestive tract. The colon receives undigested food, removes water, stores the remaining contents and then eliminates that from the body during bowel movements. There are several different types of colitis. Microscopic colitis is only visible when viewed under a microscope. According to Medicine.Net, There are two types; lymphocytic colitis and collagenous colitis. In lymphocytic colitis, there is an accumulation of lymphocytes (a type of white blood cell) within the lining of the colon. In collagenous colitis, there is an additional layer of collagen (scar tissue) just below the lining. Some experts believe that lymphocytic colitis and collagenous colitis represent different stages of the same disease.
The inflammation and the collagen probably interfere with absorption of water from the colon, and cause the diarrhea. The primary symptom of microscopic colitis is chronic, watery diarrhea.
The treatment of microscopic colitis has not been standardized because there have not been adequate large scale, prospective, placebo controlled treatment trials. I suggest you read the following article which provides a lot of information on various treatments that are being used at this time: http://www.medicinenet.com/lymphocytic_colitis/article.htm
Acid reflux, also known as Gastroesophageal Reflux Disease (GERD) occurs when acid in the stomach rises up into the esophagus. This occurs because the valve separating the contents of the stomach from the esophagus does not function properly.
This article provides a lot of information on GERD treatment, and may include information you haven't gotten from your physician.
If you go to our Colitis Community you will find information posted by other women who are also dealing with digestive disorders as well as multiple news articles. https://www.empowher.com/condition/colitis
It's not clear from your comments whether you feel your doctor is ignoring your concerns about the nausea that is now coming along with the GERD. If so I'd suggest finding another physician who will address this for you and help you find relief.
There's a lot to learn in trying to manage these conditions, and I hope you find this information helpful, and that you also hear from other women.