Sort of equivalent. "Queer" was once used as a sharp slur by many homophobes, but it's been actively reclaimed by the community and used as a badge of honor instead to remove its power as a slur. Some older members may still take offense to it just because of the historical context that they lived through, but I imagine anyone of your age or younger has zero problem with the word and probably use it themselves.
In definition, "queer" is meant to describe someone deviating from the norm. As your therapist described, in this community its often used as a catch-all for people who don't fit cleanly into the lesbian/gay/trans labeled bins. Its also frequently used when someone has more than one gender/sexuality identifications. But you're welcome to use it with only just one.
Technically, the acronym "LGBTQ+" includes Queer in itself, as the Q. But we all know that acronym sucks to use in conversation a lot lol.