You should have adequate rest / sleep 8-9 hr. Use short meals 4-5 after 2-3 hrs. For weight gain use aswagandha churna 3 gm twice a day with milk this will remove weakness problem too.
Use more of dairy product specially cheese / paneer. Include whole grain pulses in diet.
15-30 min push ups n pull ups / exercises. Don't panic
/stress it will be all right. Protinex is trusted protein powder to be used with milk./stress