Hi, Welcome to HealthcareMagic Forum.
First of all get yourself examined by a Physician to rule out the cause for so much of weight loss
. You may want to workout for at least an hour daily. You can do push ups, cardio and crunches. Eat Protein rich foods like Green leafy veggies, eggs, milk, chicken, fish and Fresh fruits. Avoid stress
and Practice Yoga
Don't go for junk food and if you smoke or drink, Quit. Regular exercise will not only increase your Muscle mass but also will increase your appetite.
Wish you Good Health, Take Care