Your weakness has due to breastfeeding so you should take such type of diet which has rich iron, calcium and minerals.
Like,
you should take pomegranate, Orange,and beetroot juice daily.
U should take papaya, dates (????) ,jaggery, boil eggs, milk.
Figs are also a great source of iron.
Usage of 3 to 4 figs daily can enhance iron in your body.