Hi,
Sorry to hear you are feeling so low. I myself have never suffered from any sort of depression, but my husband has had various levels of depression since before I met him twelve years ago, so I can sympathise with what you are going throuh!
You don't say if you are currently on any kind of treatment for this eg anti-depressants etc or if you have been diagnosed with 'depression'. But, there are lots of treatments available and it can be a bit tricky to find the right combination for you.......varying from drugs, therapy, relaxaion techniques etc!
As you say, it can be very difficult to relax, and some people don't have a lot of time for people with depression, expecting you to be able to 'just snap out of it' or to 'cheer up!' . There is certainly no shame in being depressed and there isn't as much stigma attached to it as there has been in the past, but if you see a sympathetic doctor you should be able to come up with a course of treatment that works well for you!
Here are some links that my husband has found useful in the past...
http://www.mentalhelp.net/poc/view_doc.php?id= 973&type=doc&cn=Depression%20(Unipolar)
http://www.patient.co.uk/showdoc/23068720/
http://www.depressionalliance.org/
Hope this helps
A xXx