so he doesnt have it? or he lied?

from what I've understood, he doesn't have it. Meaning that the first test that was done detected it "wrongfully" and instead of being positive it's negative. Some reasons for this could be a technical error/analysis or the participation on some experiment towards a vaccination of HIV (prob the first reason).

He didn't lied but he just rather preferred to keep quite than tell Erin/shut the rumors down.