First things first, how do you present it to your reader? If you try to do it with flashbacks, you have to be very careful to avoid flashback failure. You have to make it clear that what you are describing takes place in the story’s past. When you finish the flashback, you have make it just as clear that you are returning to the story’s present. Fail to do this and you run the risk of loosing your readers who will no longer know if they are reading about the story past or story present.
Backstory can also be a problem if you try to give the reader too much at once. More than a few lines and you, the writer, might be accused of commiting an info-dump. “Here is a ton of backstory that you need to know and I am putting it all right here.” This pulls the reader out of the story.
Last but not least, there is the problem of the fascinating backstory. Sometimes you may create such a fascinating past for your character that there is nothing exciting left for the present story. If this is the case, you might simply have decided to start your story way too late.
Take a look at the backstory that you’ve created for your character. Does it overpower the main story? Do you know how to work it in? You need it to make your character come alive so take the time to figure out how to present it to the reader.