Fast of Tisha B’Av — Breastfeeding with Migraines

On Tisha B’Av I will be two months after a very difficult birth.
I am breastfeeding and have been suffering from migraines every evening for the past week.
On a day when I do not drink, there is not enough milk for the baby, and he is unsettled.
What should I do regarding the fast, both in terms of the headaches and in terms of breastfeeding?

Shalom and blessings 

Regarding the migraines: If they continue until Tisha B’Av, take a painkiller [and if you need water in order to swallow the pill, make it bitter with salt or with several bags of chamomile tea without sugar]. If that does not help, and you are suffering to the point that you cannot function, or to the point that you need to lie in bed, you are exempt from fasting and may eat and drink as usual (Siman 554, section 6). 

Regarding breastfeeding, I am copying the instructions of our teacher, the Rav, on this matter: Breastfeeding women must fast [and they should prepare well during the two days before the fast by drinking three or four liters of sweetened beverages; after the fast as well, it is recommended to drink beverages sweetened with sugar]. However, if the baby will lack milk [and the baby needs it], or if she knows herself that the fast will harm her milk supply, she should drink as usual. 

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