Hii!
Don't worry!  This is a very common problem faced by many students. To conquer this, firstly, don't go fast while reading. Try and understand the text you are reading. It's ok if your speed goes low. And, the very important thing is concentration. You need to improve your concentration. Practice meditation. Also, try reading out loud, to get out of that anxiousness which you face while reading. Do not think that you dont understand what you are reading. Stay calm, go slow, read and understand simultaneously, concentrate on the topic. Practice this regularly and you'll be good to go.
Hope this helps.
Good luck!