I think it may be that you are around the age when you can feel self-conscious. I am a minister and very confident about speaking. Like you, I loved reading aloud when I was young, at school, in a theatre group etc. When I reached the age of 13 or 14 I became more self-conscious for a while and I rushed my way through anything I had to say/speak aloud. I got some advice at the time. I was told that I was becoming self-conscious when I focused on myself (worried about what people thought, worried about speaking in front of someone I fancied in class etc) The way to get over that is to psychologically focus on the people you are speaking in front of. More advice I can offer you is to take your time before you start to speak when you're speaking in front of people. Try to relax and look around at people and then speak slowly when you read. Think about what you are reading and what it means and think about how you can best express this to everyone in the class. Try not to think of everyone as a group but rather as individuals (many of them will be nervous too). I know it's eadier said than done - but try to relax and enjoy it.