Well that happens normally cause u are depression. Maybe if u rewind sometime in past. That friends have probably invited once or twice, or more. But u just keep saying know. And with the progressing of the time u'll start loosing contact with lots of friends. That's a typicall reaction. When u become motivated, start doing things, feeling better...you also become more in contact with people, with others, with friends...I know is hard, but try to make a efford, get a day of the week, or 1hour of a day...to keep some friends around. Like sending a message, giving a bday...take a coffee...ask you is he. Dont need to be in big parties. Get your time to get back on road. But till there...dont loose all contacts.