Any idea what the black, pepper looking flecks are in my 4 month old's stool? He was extra fussy yesterday & didn't sleep well. He is 100% breastfed.

Digested blood. Normal poop, with black flecks mixed in. The flecks are digested blood, most commonly from the baby swallowing blood from mom's sore and bleeding nipples. If u don't have a problem check for baby teething.
Wrong post. Sorry, my answer was to another post. Sorry.
Irritated Throat. You might be getting some reflux, acid from the stomach leaking into the back of your throat, often at night when you are not aware. That will irritate the throat and produce the phlegm you have. Post nasal drip might be the cause as well. Try Pepcid or an antahistamine.