People here always say "Flip it and slam it" , but that may not be the best thing for you. Everyone is different and requires a different bike fit. Most people develop the flexibility to "flip and slam it" but it does not happen overnight. Dont just do it right away because people tell you to. It is something you have to grow into and you do gradually over time.

I would start by just flipping the stem, and ride like that for a couple of months. Then maybe after that, take out one spacer every three months or so and see if it does not cause any discomfort. You did too much, too fast. Also, it may be better for you to not remove all the spacers. Try it out for yourself. Do not do anything that causes pain and discomfort just to try and act like a hardcore roadie. The best thing for you to ride safe and comfortably and to enjoy your rides, is to go with a fit that works for you. Once you are ready for a more aggressive riding position you will know.