I am so sorry you are feeling this way. I care and have related to every word you have said and know how frightening isolation and severe depression can be. How are you feeling now?
Do you see anybody for your feelings, ie. a mental health nurse or doctor or therapist? Once the depression lifts you might feel more connected to the word and the surroundings.
It's sometimes important to take care of yourself when feeling this low, especially when you feel no one cares, and when you do treat yourself gently, and well, things, can get better slowly and in time. In the meantime, do talk here if there's anything you'd like to talk about.
Please keep yourself safe.