With all above mentioned test by the DR Anjali,  also perform random sugar , TFT and B 12 . if everything is normal and still you feel so we will think of something else then.

Feeling hungry after having a big meal could be due to more stress levels .. which is normal ., happens with many individuals ... eat more proteins n less carbs which gives energy n fills ur stomach for long ., As u r feeling weak u can go in for some blood test like CBC , iron profile just to check ur haemoglobin n iron levels !