1. I'm on a dating app where you can say whether you're HIV-positive or not. But I haven't. Is that lying or just being careful?
It doesn't matter whether you are on a dating app, in a crowded bar, or in the frozen food section at Whole Foods; your status is yours disclose whenever and however you like. My personal preference is discussing HIV as soon as possible to protect myself from investing any wasted emotions. Nevertheless, your status is not a character trait or a sexual position so it is completely up to you if and when you tell someone; just as long as you aren't putting someone at risk.