Your depression can probably be treated with anti-depressive medication. Talk to a doctor you trust.
In the case of your social problems, this is something you can treat by exercise. Start with talking to people you are not afraid of and where you do not feel like an underdog. Old ladies might be a good choice. Begin showing interest for them and give them nice and interestshowing questions. You do not have to be very spiritual. People love talking about themselves.
The reason you cannot find something to say is that you are afraid. Tell them how afraid you are. You will hear many histories about other people who have also been afraid of talking in different circumstances.