It sounds like you are providing a lot of support to others but are not getting much of your own. And you have dealt with a very serious and shocking event with your friend's mother's suicide. That kind of trauma can affect you more than you realize. It can bring out a lot of fears and anxieties
From your symptoms, it sounds like you may have some mild to moderate depression with some anxiety. Anger, fear, irritation and tiredness are all symptoms. One of the telling signs is that you feel you want to sleep for a long time. That says that avoiding life is more appealing to you than facing it, indicating that you feel overwhelmed and depressed.
Because of your back pain, one of the first things you might want to do is get a medical check up. You don't want to assume that your symptoms are emotionally related if they might be at least partially because of a physical aliment. Then you would just be wasting your time getting treatment. Although most likely your symptoms have more to do with what you have been going through than not, it does not hurt to be sure. And you can at least get an answer as to what the pain in your back might be.
If you are cleared physically, you may want to consider talking to a therapist. You need support right now and it does not sound like you have much in your life at the moment. Talking to a therapist can not only help you get a more specific diagnosis, but it can provide you with ways to cope and someone to support you until you feel better.
You may also want to work on how you feel through self help. To address the agitation for example, you can try progressive relaxation. Here is a link to resources to get you started:http://www.guidetopsychology.com/pmr.htm http://www.helpguide.org/mental/depression_signs_types_diagnosis_treatment.htm http://www.helpguide.org/mental/anxiety_self_help.htm http://psychcentral.com/resources/Depression/Support_Groups/
It does not sound like you have any symptoms of PTSD, which is common after a trauma like helping your friend through her mother's death, but you may have some grief issues. You have lost or are losing significant relationships and support in the past year and you have not been able to rely on support since. Any loss can trigger grief. It does not have to be a death to bring on the symptoms. You can explore the symptoms of grief and see if it fits what you feel:http://psychcentral.com/lib/2006/the-5-stages-of-loss-and-grief/
With some support and treatment, you should feel better and be able to look forward to the future.
I hope this has helped you,