I always use kali bi for colds or hylands c plus cold. But I'm not sure if that fits yours or not.
Kali Bi is for thick mucus, usually greenish I think.
Pulsitillia is what my girls usually get for their colds. They never gag on their mucus though. It is a common cold remedy though.
Chammomilla is another one for colds. I think that is for yellow mucus and really cranky, cant be put down one red cheek.
I'm looking in my family homeopathy book. When is the cough worse or better? Night day? cold warm? What kinds of things seem to make it better or worse? Any chance it is pertussis? (tis the season).
I'm trying Nux Vomica right now, we'll see how that goes. Thanks for your help!