By going back in time I mean to begin one's story then go back a few years. Does this really work? Is it confusing? Should one just stick to starting at the beginning and moving forward with no flashbacks?
Some agents and publishers really, really hate flashbacks, if only because flashbacks get misused so often in some of the poorer and more painful manuscripts they read. For instance, start with a sentence in the present... then instantly flashback! That sort of thing is very clearly an indication you ought to start at the beginning, and/or reshuffle things around.
Also, sometimes flashbacks that you think are necessary really aren't; they would make the storyline clearer if they were arranged linearly.
A distinct advantage of starting at the beginning is that you establish context. And of course, any flashback is a scene with interesting things happening in it that drive the story forward (right?) and not merely an info dump. You may find that filling things in from the beginning is a better way to flow the story. You may find hidden parts of the story that you wouldn't find before, because you tucked them away in the unexplored area between five years ago and now.
You don't know until you try. I suggest trying it linearly first and see whether you discover anything new.
The problem with flashback is that it stops the current story dead in its tracks, and if the flashback is too long---or you didn't have enough context when you started the flashback---or if the flashback has nothing at all to do with the current part of your story---then your reader will forget what happened when they come back to the present. This is one of the abuses of flashback that make agents and editors so jaded.
I have a flashback in the current version of my first chapter, but even after five pages of establishing context, a flashback that answers a question just after the end of that context, and a mere two pages of flashback, and then a return to the current context, picking up with the same theme as the flashback...
... I rearranged it and it works out better linearly, and indeed, despite my flashback only being three weeks before, there were still interesting incidents tucked away in the three weeks that I had not explored. I've sketched out what happens, and though I will still end up skipping forward two weeks, it added depth to my original "beginning".
That may just be because I'm very poor at story telling, mind you.