Please don't do Reglan. This can cause irreversable damage to your CNS, AND it can surely cause problems in the child. Reglan inhibits the action of dopamine which allows more prolactin. Yes, it will cause a person to produce more milk, but now you have an increase in a gonatropin circulating in your system. High gonatropin hormones (hyperprolactinemia) cause infertility , shrinking breast, absence of menses,agression,hair loss,osteoporosis,heart disease,and loss of smell. In the male, in can cause low testosterone. Low testosterone can cause ALL kinds of disease and is linked to mental decline just for starters. You do not want to mess with your hormone levels which will affect your child's hormone levels. If you are taking this drug it wil be in your milk, I don't care what the doctors say. This drug is still not even really approved for anything but a real short term.
I study the endocrine system and there are reasons why children do not suckle as they should. It is more likely that you are not producing more milk because the child has a weak suck reflex or weak desire to feed, (and your body is responding accordingly to diminishing demand) rather than you having a defect in your "ability" to milk. Your goal then should not be to induce more milk but to get the child to be able to feed. A lack of desire/ability to eat/suckle/thrive is related to LOW CORTISOL hormones in the child. Low cortisol has become quite common, about epidemic I would say, although doctors will go out of their way to avoid diagnosing it.
I just responded to a mother on here last week with children who were not gaining weight or eating and indeed when she had the cortisol tested- it was LOW.