Qualifying for university is a big step in life. Congratulations for such an achievement.
Obviously, your mother is not helping the situation, therefore don't rely on her to give you support. Go to a psychologist/psychiatrist and discuss the issue with them. They know a lot about mental health and will definitely be able to help you. Regular visits are essential.
Then, you should try discuss it with your lecturer, or a university staff. Explain what is going on, so they are less harsh with you and understand what is going on.
Make some friends. Have the courage to introduce yourself to them. Friends are vital for your mental health.
Let's get to the point. But first, why can't you leave your room? I don't know why it would be such a challenge, and your answer would be appreciated. Put on some music while you walk to your lecture/tutorial, and immerse yourself in it so you don't worry about the lecture too much. And calm yourself down. Try to be rational and reasonable with your thoughts. Is it going to be the end of the world when I enter this room?
So you've entered the lecture room. Now looking at a roomful of strangers will not help with your anxiety, so again, make friends. Try and focus as much as you can. Find a suitable way to calm yourself down. It may be listening to music, breathing deeply or clearing your mind, the list goes on. Just google "ways to calm yourself down" and there'll be lots of options.
Once you've calmed down, tune yourself in. Listen as carefully as you can, and take notes. Whisk any undesirable thoughts away, and concentrate on writing down a summarized version of the lecture.
I know how scary and intimidating for you, but just try your best to keep yourself in control.
Hope this helped,