You may be having post parturition depression in addition to physical, mental exhaustion, anxiety of baby care.
Did you take iron,
calcium supplements before and now after delivery? The requirements of these 2 is increased during pregnancy and breast feeding.
Get Haemoglobin, serum vit
B12,
thyroid function tests done.
Next Steps
Take small frequent meals with fresh green vegetables fruits, nuts, whole grains milk and milk products.
Drink more water.
Try to do some pranayam regularly.
Consult online with results.