what is the meaning of "creep back in"?
the feelings were starting to creep back in.
1.what is the meaning of "creep back in"?
2.why are there two adverb {back in} after creep?
3.what are the difference between "creep back "and "creep back in"? i mean, why is adding an "in" in this phrasal verb?
4.feelings pronounce ['fi:lɪŋz] or ['fi:lɪŋs]? which one is right?

Question

what is the meaning of "creep back in"?
the feelings were starting to creep back in.
1.what is the meaning of "creep back in"?
2.why are there two adverb {back in} after creep?
3.what are the difference between "creep back "and "creep back in"?  i mean, why is adding an  "in" in this phrasal verb?
4.feelings pronounce ['fi:lɪŋz] or ['fi:lɪŋs]? which one is right?

Answer

1- creep back in: to gradually and secretly get back to you.
2- the two prepositions strengthens the meaning. 
3- Addition of "in" emphasises the meaning of the verb, feelings don't just creep back, but they creep back IN you 
4- The first one with /z/ is right since the last sound is voiced.