You don't need to admit to being deeply suicidal to get treated for depression.
People who actively intend to die and have a plan very often hide the plan from their doc and therapist in case they score enough points to qualify for an involuntary hold.
You don't even have to admit to occasional suicidal ideas. It would be smart to tell as much of the truth as you can so the doc isn't trying to make sense out of bullshit though.
Your inability to talk about suicide IRL sounds like bog standard severe situational social anxiety, which is quite common among heavy dope smokers. (As is depression).
Another common reason for not being able to talk about something is a dark secret surrounded by a large defensive zone.
In both cases treatment might start with an anti-anxiety medication and training in self-relaxation techniques.
Depression isn't always recognisable from inside.
I had ordinary moderate reactive depression once with an obvious cause and very common symptoms but didn't really realise what it was, my doctor picked it up when I went in for something else.
A few months of an antidepressant fixed it.
Decades later I was tired and under a lot of pressure at work and was quite irritable with my wife and young boy. She tried for months to get me to seek help for depression but I couldn't see it, it felt nothing like the previous time and I didn't feel bad just stressed. Again happy pills made a magical improvement. This time I needed to stay on a lowish dose for a couple of years until the stressors were removed, then I (and more importantly my family) was fine without them.
Both anxiety and depression are very treatable. There is such a thing as treatment-resistant depression, it is a very small proportion of cases though. I'd expect this sub to have a great concentration of such people.