You're not alone with this problem. In my opinion, it’s a huge problem if it interferes with your enjoyment of the reading or slows your reading down significantly. Learning a foreign language means you’re going to run into a lot of stuff that you won’t understand immediately, so if you have an obsessive need to understand absolutely everything immediately, that’s not good. I don’t have time to go into details right now, but I think you already understand that this mindset is causing you unnecessary difficulty. I say “unnecessary”, because we do have control over our mindsets, even if it seems hard at times. Even if we don’t like to admit it at times.

To clarify my previous comment: I assume that you’re using material at a suitable level for your current reading abilities (which should be slightly higher than your speaking / listening abilities). If you understand 85 to 95% of the words, that should be enough to enjoy the text and pick up new words in context. If, however you understand fewer than 80% of the words, then you should definitely find some easier material, or find some other learning method that you enjoy and works for you.