Years ago I had some advice. I find it a little ironic that it's come full circle... And indeed told its truth.
Truth being- to observe and listen. And then people will tell you exactly what they are.
That's any defence against power play, manipulation and mind fuckery. It's not always clear. There won't always be visible cues or clues as to what is going on. And there won't always be truth that you can work with. Sparing the details of motivation and agenda... Blah blah...
Truth is defined as perceived by one self. It's relative.
But when things become too muddy through thought, then the one sure thing you can know is how you feel.
That off balance, icky, anxious feeling? It means that something is wrong.
To end the questioning of reality- let the world go quiet. Take away the sounds. Feel the deep pull within you.
This is where evidence counts.
Find one point on the horizon. Do you trust your sight? Is this what you are seeing?
Find one sound out of the din. Do you know what the sound is?
More often than not you'll know what those things are. That's your safe point.
It's much like in the film Inception, where a singular object/totem is a stabilizing influence on the truth of actual reality, rather than a creation of the mind. Just as a disclaimer though, in regards to other things-you won't always be right. You'll get things wrong and make mistakes. You're human, you're meant to.
Regardless of motivation, and the insidiousness of those who make you doubt-
Remember that one rendering of perception does not make the world. It does not make yours.
Rely on health. You won't find it in doubt. Or that feeling of constriction. That's only there to tell you something isn't fitting. If you can't find what's fitting by being honest with yourself, then it's worth remembering that crazy making is exactly what it says on the tin- crazy.
Give yourself permission to think solely. And be prepared, for when things become too muddy, and unclear through thought and feeling, to know them, and then throw them away. They are transience. Not constants.
Keep looking at that horizon, keep listening, and keep observing. It'll get clear, with time.