why do I feel so alone

Why do I feel so alone? I have everyone in my life to support me and that is not enough. I sometimes I think I am selfish for feeling this way. I have been living a good life & I'm still alive and healthy. I know I am supposed to be strong and no one cares more about you then you. Why do I feel like there is nothing inside but tears. I am strong and know this life I have is better then others and others have it worst then me. The feeling that no matter what I just can't be happy. What did I do? I tried to care and help the world,is that not what I am looking for? I used to be happy when I was alone that made me strong knowing it was just me. Now I have more people in my life that I have to care about and that care about me! What will it take to get rid of this empty feeling inside? I smile on the outside, but on the inside I just don't care. I do not know should I go back into the dark hole were I was once happy because I did not have to feel? I made it so no one can interfere and leave me alone. I padded the hole of darkness so I would never care and get hurt by no one. Inside the dark place I could be who ever I wanted no one knew me so I did not care! It took me many years to get out and let things in. I climbed back out to let things in and try to feel! Maybe that is why I want to go back and disappear! knowing I would never be hurt again!