Hi,
First of all, I'm sorry you're feeling this way. Your feelings are real and you need someone to help you through this. You are worth it and owe it to yourself to get help.
I have many family members on both sides of mine and my husband's families that deal with manic depression and mental health issues. The worst thing you can do (or not do) for yourself is to think that no one can help you and then not to do anything at all. I don't know if you're a woman or a man, but in women, sometimes hormones and/or underlying medical issues can cause you to plummet into deep depression and even have suicidal thoughts, which is never the answer. Your life matters and so get immediate help through both a medical doctor( get a complete physical, blood work-up, etc.) to rule out any medical causes for your feeling this way and then get yourself into therapy with a good therapist, they do exist, I promise! Been there done that and it saved my life!! :)
here is a good link to finding a safe and qualified therapist in your area.
http://therapists.psychologytoday.com/rms/
Please do this for yourself, you are so worth it! :)
If you don't have a general practitioner (a doctor that treats a wide variety of things) then either Google your local hospital and find one or call.
Do this right away!! I promise you will come out the other side and it will get better!! You might not think so right now, but take it from someone who has felt the way you do and now has turned her life around completely! Please stay in touch and take care of yourself, okay?
Blessings....now call!!