Hello. I can understand it must be very distressing for her as well as you. It has been noticed over years that our mind and body are connected and sometimes may give rise to problems which looks like bodily problems but causes lies in the psychological process. For example. Some people when stressed develop acne, some experience constipation, some experience gastric issues and similarly pain. Individuals often gets temporary relief with any medication and problems relapse and tendency to switch doctors and look for better treatment emerge. It is one of the most researches area of topic and has treatments available in psychology
Next Steps
I think one of the most crucial step would be to convince your mother to once consult any clinical psychologist. That will help her understand her problems and then plan further treatment as well. You can consult me or any other clinical psychologist you feel is good enough. I assure you, its treatable.
Health Tips
Please take consultation once atleast that becomes important in this case. Even if you will try to say its Bcz of stress and thinking she might not be able to understand. Taking professional help, will provide her good relief.