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Till 6 months of age breast milk alone is the best for your baby.
First take care of your nutrition. Take a lot of pulses, eggs, fruits, vegetables, milk, adequate fluids, non veg (if your customs allow), saunf, dry fruits etc. Take your calcium supplements
Take adequate rest as early resumption of works will reduce your milk output.
And be confident that you can feed your child exclusively on breast milk for 6 months.
When feeding sit in a calm and private place in relaxed manner and feed your baby. If she falls asleep when she feeds, wake her up by gently stroking her feet/ ears. If you feel she is hungry after she feeds from one breast, offer her the other breast.
For inverted nipples, apart from nipple shield, you can consult your Gynae doctor and describe you syringe technique to help getting nipple out.
You should try and not worry too much about it as stress
itself can hamper milk production.
You should get her weight checked. If there is weight loss
, then she needs more milk.
Things should settle soon.
If after you've offered from both the breasts and baby still feels very hungry, as a interim measure give Lactogen milk through katori-spoon. Instructions are mentioned on tin of Lactogen. Water should be boiled first and then cooled. Wash your hands before preparing the milk. Make sure the katori-spoon have been cleaned throughly after putting them in boiling water.
You can give as much as baby takes, however, it would be advisable to offer breast first on each occasion.
All the best