Welcome to HCM! It is nice to have you join us here. Let's begin to try to address your query.
It sounds like you might be dehydrated if you are not urinating much. Let's start there. First, what color is your urine in am? If it is dark yellow with a strong smell you are probably dehydrated. The general rule of thumb is to drink 10 (8oz) cups of water throughout the day. Caffeine and hot weather may cause excessive fluid losses through sweating as well.
Second, let's take a look at why your stomach "might" be hurting. A) you are hungry and/or B) you have a
stomach ulcer, undiagnosed, and the lack of food causes a concentration of the acid in your stomach to build up and if a ulcer is there, it will hurt more. But, I have nothing to base this on - your doctor who has all your records would be more in the position of determining whether you need an upper gastrointestinal evaluation.
Next, if you desire permanent weight change, look at making permanent lifestyle changes. I don't know what restrictive calorie diet you are on, your needs, your labs or chronic health history, so it is difficult to give advice and really, to give advice one needs to assess the problem.
If you were my patient I would send you back to your doctor for some basic labs (
complete blood count, etc), get his recommendations and then visit a properly trained Dietitian to have her help you design a nutritional meal program for your condition(s), realistic goals, an individualized exercise program or referral to
Physical Therapy for a plan you can manage at your stage of MS and the Dietitian can design a supplement program should you need one based on food intake analysis and blood work.
I sincerely hope I have addressed your issue. For now, stay away from anything spicey, caffeine, pepper, alcohol so as to not aggravate yourself. Count your fluid intake and be consistent, follow-up with doctor and dietitian.
My sincere wishes for an improvement in your health, Kathryn Shattler, MS,RDN