I am sorry that you are having a difficult day. Shed those tears, let them all out, feel the pain and release it. Tears help us heal. I'm not making excuses for your mother, but she may not know what to say or do for you. Maybe she thinks you need to get this all out of yours system. She may think that waiting until you aren't so emotional is the best way to be there for you. Have you tried to talk to her...it could be that she is waiting for you to come to her.
I know how it feels, my mother was the same way, but when I finally exhausted myself and my tear ducts had run dry, she was there to listen and a shoulder to lean on.
Please take care of yourself.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.