Thank you so much, everyone, for your really excellent info and advice.
I am inclining towards trying a big detox (saunas etc) and some careful experimentation with supplements or herbals.
I know I should try to get that serotonin test, but I just cannot face yet another medical investigation right now!
I think Lala and others made the very good point that antibiotics have a "depressive" effect on the body, which is not the same thing as depression.
My sister suggested I might like to try Liquorice tea. Do you guys think that is safe? She said (she she studies this stuff) that liquorice is a stronger natural antidepressant than St John’s Wort, which is ranked alongside prozac etc for efficacy, but that it doesn’t have all the horrid side-effects. Perhaps because of the slightly different effects they have or don’t have on serotonin as explained in this peculiar research article about depressed Swiss mice having to go swimming.
http://www.ncbi.nlm.nih.gov/pubmed/16443316
Leaves, PLEASE could you post a link to the online checklists for deficiencies in the nutrients that you mentioned? Thx.