Where to Begin?

(Warning, this post tends to ramble, much like I do at times when trying to determine a direction)

I am about 38% of the way through my latest WIP. It is a sequel to a story I have been sending out and entering in contests. I originally started with a Prologue to give a little background. I then dumped that to start at a more exciting and action filled spot. However, now I find I am adding in backstory (more than I like, and probably readers as well).

So, now I am wondering if I acutally need to start the story earlier, at another exciting point to avoid all of the backstory. But, the delimma with this is I will have approximately two chapters in one year and the third chapter will start two years later. I am not sure I want to do that if readers would be bothered by it.

This is not unusual for me. However, I usually dump the first to third chapters because a lot of the time it takes me that long to get into the flow of the story and I realize I was only practicing and getting to know my characters for the first 20+ pages. This is the first time I've thought about actually starting earlier to add on instead of dumping.

Do you ever have the problem of starting your story at one point and then realize it needs to be started earlier or later, only to find yourself wondering if you should change it again? From a reader's perspective, how do you feel about stories that jump two years, as long as it is still a smooth transition?