Even though he made jokes about taking ecstasy on “Late Night With Jimmy Fallon,” comic Artie Lange says he’s never been clean this long — eight months — having kicked a four-year heroin addiction. Still, he’s terrified of doing a reality show. “They offered me 200 grand to do ‘Celebrity Rehab,’ ” he told The Post’s Mandy Stadtmiller as he prepared for his New York Comedy Festival show. “I love Dr. Drew . . . but I don’t think that’s helping Jeff Conaway . . . They said it was about me getting better, but if I relapsed, they’re not going to air that? . . . My mother knows I’ve done coke, but she’s never seen me do it.” Lange says he hasn’t done cocaine since June 14, 1997: “I just got tired of it. I got to a point where this is killing me . . . so I think I’ve got to that point with heroin . . . My thought on heroin is: It doesn’t make you forget your problems, it does something even better. It makes you not care about them at all.”