Could you try talking to your mum again and keep telling her your really depressed and would like to see another therapist because pachyderm is right... you need someone to listen to you and even if you can't make sense of why you're feeling like this it's quite possible that with a bit of help you may find that answer and then you can concentrate on fixing that. It all takes time, but the sooner it starts, the sooner it ends?
I wish you all the best, just remember you can talk all you want on here and there'll be someone who'll listen,
Molly