Back-story is essential to motivate the plot and storyline of a novel.
It adds flesh to the main character/characters.
The placement of Back-story will vary according the genre of a novel.
The back-story of my protagonist started on Page 43 of my chivalric romance.
Did your Back-story start at the beginning or after numerous chapters?
'Backstory' is one of those things that can make or break a novel, IMO. Too much and you can kill it stone dead, as your reader switches off in the midst of pages and pages of what happened so long before as to be largely irrelevant.
I try to hide it by offering hints or suggestions as the story progresses. A character's thought or action. Maybe a conversation. Straight explanations of a character or event's history should be included only if absolutely necessary because it usually makes boring reading.
I should talk - my second book is 43 chapters of backstory between prologue and epilogue ;)
I've never manged to get far enough, or write enough to get to the stage of including a back story!
Man, I suck.
Half way in I started to bring in the back story.
In the first half I wanted to look closely at how the family in my story are affected by a suicide. I wanted to build an intimate picture of their reactions.
Only once this had been developed did I bring in the "analysis" part. The "why did he do it" aspect.
Which helped to bring about the resolution as the family move on from their grief.
It was a very deliberate set of events to lay it out this way.