Hi, I'd like to help you with your question.
No, you are fine. There is nothing wrong with you You are experiencing grief and reacting to your loss.
Loss causes people to go through the stages of grief. Some people go through all stages, others through only some. Depending on the relationship of the person to you, you may grieve for a short time or a long time. Since you cared for your mother for so long, you were close to her on a daily basis. You may have been close to her emotionally as well. Her absence from your life is huge. So your loss if felt more deeply.
What you are experiencing with hearing your mother call out is called preoccupation. It comes from the grief you are experiencing. You are thinking of your mother daily and focused on how you feel. This causes you to think you hear her. You are having a very common reaction and it is nothing to worry about. People who are under a lot of stress often report hearing voices. It is thought that at any given time, one out of fifty adults report hearing voices and those going through bereavement are especially prone. If you were going mad, you would have other symptoms and you would not be as worried as you are about it. People who truly have severe mental illnesses usually lack the insight to notice that they are having symptoms. So you are just fine.
Loss and grief also accompany other feelings that most people are not aware of. Guilt (survivors guilt or guilt for not being there more, for example), anger (why did they have to leave me?), envy (why does she get to have her mother and I don't?), and relief (if the person was suffering or because they needed a lot of care). These feelings, if unresolved, can cause your grief to continue longer than normal.
You can also get stuck in one of the stages of grief. Some people remain angry or others depressed. Working through grief takes time and effort. Getting stuck means that more effort and support is needed so you can feel better.
There are many ways you can help yourself feel better and move on. You will never forget your mother and you may always feel sad when you think of her, but the daily grief will lessen so you can go forward.
Enlist support- family, friends and others who you know can help you reminisce about your mother and remember the good times
Express your feelings- write, talk or spend time artistically expressing how you feel about your mother. It helps to put your feelings out there so you can take action with your grief.
Keep mementos- have a box or special place you keep your favorite things about your mother. Go there and think of her, then allow yourself to move on the rest of the day. It gives you a place to grieve, instead of feeling you need to grieve all day.
Use music and exercise- work out to help yourself feel better and sleep better, and use music to lift your mood.
Keep in mind that this will pass- you can move on and feel better. Very few people mourn forever and usually it is those who choose not to help themselves.
Consider counseling if you still feel at a loss and hearing your mother continues to bother you. Seeing a therapist can help give you the boost you need to move through your grief. It also gives you time to talk about your mother to someone who is there for you.
You can also work on this at home. Here are some resources to get you started:
Healing After Loss: Daily Meditations For Working Through Grief by Martha Whitmore Hickman
On Grief and Grieving: Finding the Meaning of Grief Through the Five Stages of Loss by Elisabeth Kubler-Ross and David Kessler
When there Are No Words: Finding Your Way to Cope with Loss and Grief by Charlie Walton
You can find these books on Amazon.com or your local library may have them for you.
Also consider support groups. There are listings in the link above. It would give you a chance to talk to others who understand your loss.
I hope this has helped you,