I'm posting this on an anonymous account also because of the sensitive nature of the subject.
YOU ARE NOT ALONE.
All of these armchair medical professionals will never know what it is really like to have depression. All of their advice is all well and dandy for situational depression, but from your brief description that is not the case. Vitamin D, get in the sun, structure, blah blah blah. Depression is a real medical condition resulting from chemical imbalances that is treatable and you can live a happy normal life with treatment. You can continue to be an instructor with the possibility to be a better instructor than half of the people here giving ignorant opinions on your medical condition.
Now to answer your question. An official diagnosis in itself will not prevent you from getting your class 3 medical. Now, reporting this diagnosis to the FAA will jeopardize getting your medical.
Now for my opinion and what I did myself. I'm not suggesting you do this but this is what I did. I started out seeing a therapist who recommended an anti-depressant. I then went to my doctor and was prescribed said medication. It has done wonders for me and I lead a "normal" life. I've been on the medication for over 4 years now with no ill effects. For my flight medical I fail to mention my depression or medication. I also do not list the prescribing doctor as my physician so that if they start looking into my medical history it will be difficult or impossible to find. Again, I do not suggest doing this, and the consequences of this could blow up in my face one day, but I am able to continue to hold my flight medical. I also consider myself to be a safer instructor than many of the "normal" instructors that I meet.
There are many out there like us but probably won't post anything like this to avoid ridicule.
Good luck,
HealthyTI
