Hi, I'd like to help you with your question.
It sounds like you need to at least rule out Bipolar disorder. Bipolar disorder is usually characterized by mood swings from depression to extreme happiness. The mood swings can be for days, weeks or months. Often, the person experiences such extreme changes that their ability to lead a normal life is greatly affected.
When you feel depressed, you may not be able to get out of bed. You feel down and lethargic. When your mood is up, you may go on spending sprees, not be able to sleep and feel up all the time.
There is no known cause for Bipolar but it does tend to run in families.
Rage and anger can be part of Bipolar, but it is not a significant symptom of the disorder. It usually results from the frustration of dealing with the symptoms of Bipolar.
What you may have is depression. What type is difficult to tell without an evaluation. But it could either be a brain chemical imbalance or it could be caused by your circumstances. People who have extreme amounts of stress can react with anger, even to the point of rage. Another possible cause is something in your background. For example, being abused as a child often causes multiple emotional issues in adulthood, including anger and rage.
The best option for you is to get an evaluation by a trained therapist or psychiatrist. Talk to your doctor about referring you to someone who is qualified to help. Or if you have a local community mental health center, they may be able to help.
An evaluation can help break down your symptoms and give you an answer to what diagnosis you are dealing with. You can then start treatment, with either medications, therapy or both. Finding the origin of your feelings will help guide you on how to resolve your depression and anger and help you find a better way to cope.
Also, you may want to consider finding ways to relieve some of the stress you are under. You are in a high stress career and you also are responsible for caring for an ill relative. Both are very stressful and can contribute if not cause depression and anger. If you can find assistance for your grandmother, someone to help you even for a few hours a day, that would help give you a break. Also, if there are any elderly assistance programs in your area that can help, contact them. Even hiring a nurse a few times a week so you can relax and do something you enjoy. Talking to friends and family can also make a big difference.
Here are some resources to help you:
Undoing Depression: What Therapy Doesn't Teach You and Medication Can't Give You by Richard O'Connor
The Cognitive Behavioral Workbook for Depression: A Step-by-step Program (Workbook) by William J. Knaus and Albert Ellis
The Relaxation & Stress Reduction Workbook (New Harbinger Self-Help Workbook) by ***** *****, Elizabeth Robbins Eshelman, Matthew McKay and Patrick Fanning
A Mindfulness-Based Stress Reduction Workbook by Bob Stahl and Elisha Goldstein
You can find these books on Amazon.com or your local library may have them for you.
I hope this helps. Let me know if you have further questions,