Bad Appetite, Low Weight, Inability To Eat Spice, On Synthetic Analogue Steroids And Ayurvedic Medication. Help?

Dear Sir, Greeting! I m a 30 yrs old male (currently a research scholar). I ve a moderately lean built with a body weight of around 64 Kg. More so I m keen to increase my weight to around normal (at least 4-6 Kg extra) but the problem is that I m skeptical about health/ protein supplements and more so I have a bad appetite to gain weight naturally. I also remain chronically constipated often with seldom having to go more than twice in a day (usually once in two days on an average or even less frequently sometimes), vegetarian, cann t eat spice food (probably also taking a toll on me in a hostel life) and cann t eat frequent diets in a day (poorly defined & busy for nothing sort of lifestyle of a PhD scholar). I m interested in gaining general health & weight naturally. Although I m a doctoral student of pharmaceutical science still I don t advocate the use of health/protein supplements as they may still contain synthetic weight gainers including synthetic steroid analogs. Due to lack of a good appetite and general feeling of weakness I sometime feel unable to meet my daily tasks. Further I have started developing a depressive attitude towards life and a lifestyle, which almost lacks adequate physical work. I need your help to suggest me a solution based on principles of ayurveda to gain what I feel lacking.