You know, most people who feel depressed do start to isolate themselves. I think we have all been there to some degree or other and Im sure its to do with feelings of self worth and the need to protect from further hurt and difficult situations. i.e. if isolated there is no need to live up to other people's expectations or to feel that you have to put on a "face" for their benefit.
But you know what, true friends will let you be yourself and will understand and stand by you. Also the more you isolate yourself the less opportunity there is for others to help and pray for you and the harder it gets to be with other people. CC is useful but you need face to face contact as well.
I have a little 40 day devotional book called stepping stones to freedom, which really helped me a while back. I dont know what you think (I know you don't know me very well) but maybe I can post it to you if are ok with emailing your address to me via CC (If you would rather not do that, then thats fine).
Or you might want to order it yourself from the following website, I have found the USA version of the website for you. You just need to click on the headings below:
Welcome to Heartcry for Change USA
Welcome to the Heartcry for Change USA Shop
Rachel Hickson the founder is brilliant she has been to our church on a couple of occasions in the UK and has a real ministry to women especially.
She is a very clever scientist a phyisicist if I remember rightly, but she is so real and down to earth.
God Bless x