Abby Lee Miller fought back tears as she left the halfway house where she's serving the end of her prison sentence due to an apparent medical issue ... the second in less than 24 hours.
Abby's seen walking out of the facility toward a car picking her up when she's asked how she's feeling, but she signals she can't answer ... and appears to be in pain. We're told she was heading back to the hospital for treatment.
We broke the story ... Abby also left the Residential Reentry Center Tuesday afternoon in an ambulance after medics responded to a call for an "unspecified medical complaint." Her weight loss surgeon, Dr. Russo, explained the back and thyroid issues she is dealing with.