Aw, hon, I'm so sorry
As you can see, you're not alone, either in your experience (so many people have lost loved ones; I lost my brother about the same time you lost your mom) or in people's willingness to listen.
One thing I found is that talking to people who have been through a loss really can help. Have you looked for a grief support group? One of the hardest things about losing my brother was feeling so isolated, like I was surrounded by people who just didn't understand, not because they're bad or insensitive, but just because grief over a death is something that you really don't understand till you've had to go through it yourself.
Another thing that helped me was writing a journal to my brother. When I wanted to talk to him, I just wrote it down. It might help you to express the things you're feeling to your mother, even if it's only writing it down as though you were saying it to her.
Just know that everyone's experience is a little different, and takes different amounts of time. But you will get through this. Sometimes that thought was the most depressing, that some day I wouldn't hurt any more, that I'd just be used to him being gone. But I haven't gotten used to it, really, I've just come to accept it more, and the hurt is less like a shock and something I resist than an old friend who reminds me what I loved and miss about my brother.
You can PM me any time if you want to chat.