I felt like you when my father died. My mum died young my brother committed suicide and although I had a family, nobody understood how it felt to be me. I felt terrible until I got a card from my office which had "Happy Birthday" crossed out and "Sorry" written over the top and inside was the explanation - I just got sent out to get a card for you!! I suddenly saw the funny side and started giggling. They knew me well enough to know that I would find it funny. after all the sympathy cards, that was the one that got me out of the doldrums! It will happen for you too.
You will get through this. If you are strong enough to be self sufficient, you are strong enough to recognise that there is also a place in your life for a good friend or two because there are times when you just need another human being to empathise with you and give you a hug, and you are also strong enough to make that happen. Join something (or everything then drop stuff you don't like so much) and instead of being self sufficient, help others - it helps you in the long run. The u3a has lots of interest groups you could join - walking, books, Spanish, Scrabble, Canasta, Photography - have a look at the website and just get in touch. Or you could volunteer to help in a school or charity shop.