A good story happens when you get your character down that blasted rabbit hole. The plot is just a vehicle for the characters. When they are dealing with problems, they have to reveal themselves for who they are. Just keep them moving and let them bounce off each other.
Start now. Don’t worry about the past. Flashbacks should set off alarm bells that there is something not quite right with your story. Instead, think of Lewis Carroll’s ‘Alice in Wonderland’. By the end of page one Alice is down the rabbit hole.