I have the original ipad and have lost my contacts three times, each time I have reentered, syncing each time and backuping my ipad. I'm considering upgrading to the latest ipad however will I have the same problem?

I have the original ipad, I sync to a pc using windows 7. I have lost my contacts, I did everything I read about and couldn't retrieve them, I then entered what I could mannualy back into contacts. I have completed this task twice and now for the third time I've lost my contacts. I am beyond frustration. I'm afraid that if I upgrade to the latest ipad the same thing will happen because I use the same pc for sync and backup. What do you think?