Ask your health food store for a good meal replacement that is good for digestion. There are many to choose from.
Have you been tested for Candida? It can cause some of the symptoms you are having, especially the digestion issues.
Complan comes to mind. It is not a weight loss formula.
This is the write up on Complan:
Complan is specially designed to provide a balanced nutritional meal when you may be experiencing a lack of appetite. Each drink provides essential vitamins and minerals such as vitamin C and iron to support immunity, protein for muscle growth and maintenance, B vitamins to release energy as well as calcium and vitamin D to promote strong bones. Complan drinks are also free from artificial colours, preservatives and sweeteners, while also being gluten-free and suitable for vegetarians.
If you type Complan in the address bar, information will come up about the product. Many years ago you could only get one type that was mixed with milk or water, but now there are different flavours available.
If you are not able to buy this in your country, you may be able to purchase it through the internet.
Ask your doctor if he is able to give you a prescription for a meal replacement.
Best wishes.