I loose my weight day by day and feeling tired.

There can be several reasons which may cause a pain the stomach during intercourse especially during, before and after the menstruation period. Almost every woman feels pain during intercourse at the time of deep penetration. If you are having deep abdominal pains on a regular basis during intercour....

Take high fiber low fat diet. Drink lot of water everyday. Take small and frequent meals at regular intervals of 2-3 hrs. Avoid outside food completely. Do crunches and pushups daily to reduce belly fat. Ask me directly for customized diet plan for you. 

please read the link below for detailed information on the condition. https://ghr.nlm.nih.gov/condition/bardet-biedl-syndrome