I am 38 years old working mother living in joint family. I lost interest in everything including sex. I am unable to enjoy special days, festivals not even find interest in dressing up. What is wrong with me?

Maybe you have got depression or a depressive phase. It might occure when you feel overwhelmed or exhausted because of the work your are doing every day. Taking some time to relax, a vacation, or doing some daily deeds like yoga, relaxing tasks might help. If you have a trusting partner, you might as well ask him to help you out with the children or household etc. to figure out how to find joy in life again. You might as well talk with a therapist if it gets worse or stagnates. I hope you will get better soon.