even though I dont understand your doubt fully, I will attempt to point out the common problem encountered with participles:
#
participles are NOT REALLY VERBS : a participle is kind of a hybrid between a verb and an adjective.
#it has to qualify a noun or pronoun
# there are two kinds of participles: past(endind in -ed,-n-t,-en,-d)- believed,stolen,meant, driven,....
present(-ing) : believing, stealing, meaning, driving
in your example
I had been expecting such reply., 'had been expecting' is the past-perfect-continuous form . 'expecting' is not uded as a participle here, but as a verb as it does not describe a noun or pronoun. 'expecting such a reply, he only smiled'.....here expecting is used as a participle as it is describing the pronoun 'he'. (smiled is the verb here..and the sentence is in simple past)
what i am trying to say is ,even though -ing words are known as
present participle forms of a verb, they are used in two ways: as a
(1)
continuos tense verb (where you need to use be forms....I was expecting....i had been expecting...I am expecting)
(2) as a describing word(adjective. or, truly., as a participle.)
.
hope this helps.