That's pretty interesting that you say your condition alternates between OCD and Depression, I think I may know why that is but it's only a theory.
Basically what antidepressants do is recycle the same serotonin in your brain so that it stays there longer, but it does'nt actually add any new serotonin into your brain. There are dietary supplements you can take which can actually add new serotonin into your brain (L-Tryptophan, 5-HTP), the way we get serotonin is actually through our diet but your diet could be lacking in it. There are also supplements to increase GABA, some of them being Valerian root, Kava and Picamilon (probably the best one but takes longer to work).
If there is hardly any serotonin in your brain to start with then antidepressants may not work as they only recycle the serotonin already in your brain.
GABA and serotonin work together and if the levels of one of them are decreased, then it will usually affect the both.
Have a look up about the supplements but you would need to be very careful taking 5-HTP or L-Tryptophan if you are already on an antidepressant right now. To start with I'd recommend you get Valerian which is easily available in most chemists or health food shops and let us know if it helps at all with the stress.
I would say both serotonin deficiency and GABA deficiency fit me pretty well. My stress levels are off the charts mostly because I am an extreme perfectionist when it comes to my schoolwork.
Nothing brought on the depression. There has been no deaths, abuse or anything traumatizing. When my OCD symptoms flare it seems that my depression symptoms reduce and visa versa.
All the medications you listed all help increase either serotonin or dopamine (brain neurotransmitters which regulate mood) but there are other neurotransmitters which can cause depression if your brain does'nt have enough of them.
The two other main neurotransmitters are GABA and endorphins.
Have you ever taken valium or a benzo or one of the over the counter relaxants like valerian or kava kava? These help increase GABA.
There is also a natural supplement called D-Phenylalanine that helps increase endorphins.
Go to this webpage which has lists of the symptoms of deficiency for all the neurotransmitters and tell me which one matches up the most with how you feel:
http://www.nutritional-healing.com.au/content/articles-content.php?heading=Neurotransmitter%20Deficiency%20and%20Excess%20Symptoms
Did you have certain things happen in your life that started this depression? Or was your life really good and this unexplained depression started? At any point during the past 9 years, did you have any relief from depression?