It's better to read out loud. When you start to pay attention to the way you sound, calmly bring your thoughts back to the reading. You're going to be reading the same thing over and over, so don't worry so much about not catching everything.
This seems to be a common problem, as now four of us have said that they experienced it. It took me about 4 weeks before I could read out loud to myself, in my room with no one else in the house, without a lot of self-consciousness. But I did accomplish this, and it felt very good when I did.