I need to find the courage to open my mouth

You might be able to reduce your anxiety by preparing in advance for speaking situations. Reading, listening and writing all help to prepare you for speech. Get used to hearing yourself speak by reading out loud and talking to yourself, inwardly or outwardly. Try speaking in one-to-one situations before you speak up in public. Gradually you will become more courageous and able to enjoy taking part in all sorts of discussions.