It looks  like there is defecit in your calorie  intake, you have to add atleast  500 to 750 calories  on a everyday  basis  and they should  be mainly from your protein  source. This will help you to gain approximately 1/2 to 750gms. This increased intake should be well substantiated with optimum combination of  muscle building  activity.

Yes you need to add calories in diet. Try to manage eating dencer meals. A Smoothee with Protein supplement can be taken. Or foods like milkshake Dry fruit ladoo or Churma ladoo can be taken. Try to manage exercise and have a good pre and post workout snacks to build muscle mass and increase weight. Consult me on Practo online consultation for a personalized diet plan