You should make some sort of adjustments in your food - style and ensure that you are enjoying a sound sleep during night. There are a few additional points which must be taken into consideration if you want to put significant weight.
1) First of all, you need to get your blood - report from a reputed pathological labs with respect to liver - function test and thyroid test. In case of dysfunction of liver, the nutrients of food will not be properly absorbed and as a result, you may not gain weight.
Supposing that you are suffering from hyper thyroidism, you would loose weight in due course. Any abnormality in this regard can be corrected with the appointment of your physician.
2) In Ayurveda, Aswagandha - powder is available. This powder roughly one teaspoon should be dissolved in Luke - warm milk and should be consumed prior to going to bed in night. Continious use of the same for two months would help you in gaining weight since this herb contains abundant amount of Iron, Calcium, Phosphorus and other valuable constituents helpful in gaining weight.
3) Include some healthy fats and Protine in your meal such as clarified butter, Cheese, , eggs and dry nuts like Cashews and Walnuts etc. A regular incorporation of these items will certainly be helpful in registering weight.
4) Involve in regular exercise such as brisk walking for thirty minutes regularly and even stretching exercises would be helpful to you.
5) Stress should managed within a reasonable limit. A few leaves Tulasi if chewed early in the morning in empty stomach would prove to be an excellent immunity - booster.