Michael Jackson: Do You Want Fries With That?

Michael Jackson was so worried he couldn't perform his London concerts in 2009 ... he worried out loud he would end up working behind the counter at McDonald's. 

Karen Faye -- Michael's hairstylist for a quarter century -- was interviewed by LAPD detectives days after MJ died ... and TMZ has learned what she said to police.

Faye told cops, "He was scared to death because AEG was funding everything.  He said he would have to work at McDonalds if he didn't do these shows."

Faye also told investigators she believed Michael was "self-sabotaging" with drugs because he couldn't do all 50 shows.  Faye said she believed Michael needed psychological help because he was losing so much weight -- adding, "I thought he was under the influence of something."

Faye says Michael's assistant told her MJ was seeing Dr. Arnold Klein 3 to 4 times a week and was exhibiting signs of drug use.  Days before Michael died, when MJ seemed to be more lucid, she asked Michael's manager if he knew why Michael had taken a turn for the better.  His response, according to Faye -- "'Cause Klein is out of town."