Be very careful about seeking medical help for depression, there have been cases on here where drivers have lost their HGV entitlement because of doctors bubbling them up to the DVLA, and DVLA taking the view that it is mental illness.
Exercise, sunlight and having people to talk to all help. There is non-prescription medication you can take, 5HTP helps with depression (and insomnia), as does valerian. Both are available on ebay.
I do think it helps to remember that depression is fairly common, part of the “human condition” really, in fact, I think there’s something wrong with people who don’t suffer from it! Anybody who does not dwell on past mistakes for example, is destined to repeat them. Anybody who does not feel anxiety about the future is not making the best preparations for it.
Just my thoughts, and I certainly don’t hold myself up as an expert on the subject, just “school of life” stuff really. Good luck.