jennifer,
caeden is adorable!
when micah was as young as your lo i couldn't tell either. but now he's 4.5mo and i can clearly tell the difference.
mantra cry sounds like it's coming from the throat, and it sounds like baby is complaining or moaning, not "real" crying. it also usually does not involve tears. it's called mantra b.c usually it sounds like the same sound over and over. "real" crying sounds like it's coming from the chest, screaming, and with tears. trust your instinct - if it sounds like baby needs you, he probably does.
how long are you keeping him awake? he might be overtired and therefore can't fall asleep easily. definitely try closing curtains/blinds, going into a dark room, swaddling. etc. or he might be going through a growth spurt.
hope that helps.
selena