I do not trust what Donald Trump says, due to his incessant lying.

Tonight, his personal White House physician said, "This evening I received confirmation that both President Trump and First Lady Melania Trump have tested positive for the SARS-CoV-2 virus."

That means that he himself has not conducted a test on the president and First Lady.
Why not? Was he...doing something else?

The likelihood of Donald Trump just trying to mow over today's bad news (his shamefully-childish debate performance, recordings of Melania being pretty terrible, the Proud Boys, Brad Parscale) is...enormous.
As of this moment, they've changed the story.

The likelihood that he takes some time and then says, "I had the sniffles. It's not that bad. Don't worry about masks. Open your schools. Play football. I've done a great job," is...enormous.