Your progress isn’t reset. If you look at your public portfolio, you will see all of the lessons you’ve completed. There will be several lessons on the curriculum page that are not marked as completed, especially in the early sections. That’s because they’re new. You don’t have to do any of them, whether they’re similar to things that you’ve done before.
While you have done some challenges that used regular expressions or object oriented programming, they are not the same ones that are in these sections of the new curriculum. There are some that are very similar to old challenges in that they are intended to teach the same lesson, but the content has changed enough that old challenges don’t directly translate. Remember that none of these are required, so you don’t have to do the new challenges if you already understand the concepts being introduced.