The same thing happened to me -- my breasts felt relatively flabby and did not engorge as they had in the past, and I thought it surely meant the end of breastfeeding. Have no fear. This is apparently normal. I read in one of my breastfeeding books that at around four months of established breastfeeding, this change occurs but it does not mean you are drying up. It does mean that your breasts are more experienced at lactation and enter a new phase in which (1) breast milk if not consumed is "reabsorbed" by your body (which is why you do not get engorged) and (2) in which the let down is triggered within two minutes of a feeding (new experience for baby that the milk is not just sitting there).
As for the crying, apparently one thing that can trigger let down (in addition to suckling) is a baby's cry (not necessarily yours). So, your baby's cries are actually helpful, even though she does not know it. And, yes, you may not be producing enough for your baby right now, since she is probably going through a growth surge or is hitting a new feeding plateau. But that should right itself within a few days. Supplementing a bit of formula will not destroy your breastfeeding relationship while your more mature supply level is being established.
And back to empty breasts - I don't feed my girl from 6:30 p.m. until 7:00 a.m. (She is seven months and takes breast milk in a bottle for her dream feed since the bottle requires so little effort on her part and therefore does not wake her up). I have no engorgement whatsoever when I wake up, but the milk comes once she starts feeding first thing in the morning. So, this change you are experiencing, from my experience, is normal.