Can it be possible that you don't produce enough milk to breastfeed?
Yes, some people doesn't have enough milk. \
When a mare is in foal they typically dont begin to produce collostrum (what the foal will drink until the true 'milk' is created a few days or week after it is born) until 1-3 days before the foal is born. Some mares will produce days, and even possible weeks in advance. It is also possible to not produce the first milk until after the foal is born.