It is hard to deal with depression and grief at times. Counceling, meditation, aromatherapy, and sometimes just a good old cry it out session can help. Try to focus on the good times you had, when it really hits you hard. Your mother would not want to see you sad from her loss. And remember, you are not alone. Eventually we all lose someone in life. Life is not meant to be eternal.
There are many ways you could try to speak with her. Meditation, prayer, or with a medium or tool such as a spirit board. I personally prefer meditating for this. I often think of my grandparents or my friend that I lost. When it gets to be too much I remember a few encouraging words from them, and focus on that for a meditation. Or simply recreate them through strong visualization. It is my way of keeping them alive in memory, and helps to calm the grief. Blessings to you. It will get better in time