HOT MESS PETE BACK IN REHAB!

FRAGILE funnyman Pete Davidson was teetering on the brink of a nervous breakdown and left with little choice but to check himself into a psychiatric facility in yet another desperate attempt to get sober, sources tell The National ENQUIRER!

- 

Ever since the 30-year-old Saturday Night Live alum split from Outer Banks stunner Madelyn Cline, 27, in July, his behavior has gotten increasingly unpredictable and erratic, insiders report.

"Pete took the breakup very hard," says one snitch. "For just a blink of an eye, he may have thought she was the one. They burned so brightly together and had so much in common."

The serial lothario has long battled substance-abuse issues, including an addiction to the dangerous hallucinogen ketamine, which he once claimed to have taken every day for four years. He's been in rehab at least seven times before, with one recent stretch ending last September.