My mom age 49 years have myoma from past five years and anaemic due to heavy bleeding, and now having weight loss, can you please tell why?

Fibroids. Uterine myomas (leiomyomas, fibroids) actually start in your 20's usually and grow with time as long as you are producing sufficient estrogen. If her anemia is severe enough she might experience some weight loss associated with it or it could be due to other problems like thyroid issues, diabetes, etc. She should have a gynecologist evaluate her.