Selena Gomez's Drug & Rehab Lies Exposed!

RadarOnline.com has learned that recently rehabbed Selena Gomez is trying to pin her latest bout of problems on her Lupus  — but an insider insists the singer "is full of s**t!"

"It is terrible that she has Lupus," a chronic inflammatory disease that occurs when the body's immune system attacks its own organs and tissues, "but she is using this as an excuse for everything lately and the truth is that she is just a mess right now," explained a source. "She has been feeling completely alone lately."

As RadarOnline.com exclusively reported, the shocking June murder of 24-year-old Gomez's close friend, Christina Grimmie, contributed to send her "spiraling" into drug abuse.

An insider revealed that Gomez had begun using a potentially deadly cocktail of "Lunesta, Ambien, Klonopin and Xanax" before loved ones staged a desperate intervention and checked her into rehab.

"Everyone close to her is worried because she seems to be back to old behavior," said the source of Gomez, who did a previous stint in treatment back in 2014.