I have some advice for you, feel free to leave it, if you think you don't agree with them....
First your depression.....now if your depressive symptoms are beginning to effect your day to day routine, it might be an good idea to visit your GP and see what can be done in terms of treatment, both psychologically (Counselling) or physically (Medications)....the reason I say this is because some of the symptoms you are experiencing may come across as lack of interest and enthusiasm to employers in interview, who would not know about your illness.
In terms of your unemployment, I will think about the following points...
-- Can I perhaps take up employment in an slightly different sector than Engineering or another sector of Engineering?
-- Are there any opportunities abroad, in particular countries where engineers are in high demand.
-- Are all my experience on my CV up to date?
--Is there an chance that my salary expectation is too high?