Watched The Substance
Demi Moore is the star of a workout show (they still make those?) who gets fired by the network on her 50th birthday ("At 50, it ends" says a repulsive exec played by Dennis Quaid). Demi gets in a car crash, escapes unscathed and a doctor hooks her up with a black market drug called MOVIE TITLE, which basically promises eternal youth. What it does is make you birth a young, hot(ter) version of yourself through a large gash on your back (see Alien: Covenant). While one version of the person is conscious, the other is unconscious and plugged to an IV food pack that's good for 7 days. There's a switch every 7 days, or else.
So Demi Moore births her younger self (Margaret Qualley, in everything these days), reclaims her old job under a new persona and all is well until the switcheroo system starts wearing thin on the older self, who essentially locks herself up and makes herself wait for every other week to actually live her life. So she starts cutting corners, like overstaying in one body, with mortifying body horror effects, which creates tension between the older and younger self (even though they're technically the same person). Every now and then Demi calls a hotline asking for help, complaining about The Other, and she's always reminded that "You're the same" and in control.
The movie's been compared to the world of Cronenberg, Carpenter, Lynch, Haneke. Ok, I definitely see Cronenberg, and maybe a bit of Carpenter, but frankly the movie ends up owing its biggest debt to those gross and cheesy Frank Hennenlotter movies from the 80s.