That’s a long time. Well, thankfully, we don’t have to tell even our closest friends everything. You’re always free to compartmentalize and share different things with people who you think are most likely to help you. I don’t think there’s any one person with whom I share everything, personally, at least at the moment.
Some, perhaps many, would say, “As you should.”
Trust is a big deal. Trust is, basically, belief in the future presence of another’s support—whether emotional, or whatever you want to define it as, which can change per person.
This is why solid, trustworthy friendships take soooo long to develop, even literal years; they are mutual support, and people are so different that the best way to uncover this (since you certainly can’t force it) is through time and lesser experiences, which sort of double as tests of trustworthiness. While I’ve lethargically been on my way out of Christianity for years now, Luke 16:10 comes to mind.
Small acts of leaning should be reciprocated. If not, back off in both depth and frequency of communication and seek out others who do reciprocate.
I suppose I passively assess based on simply how the other person responds to questions of any kind involving my or their life, or my decisions. If there is a general trend of negativity, and your efforts to change it aren’t working, then it’s time to step back and look elsewhere.