Justin Timberlake 'Not Doing S***' After Tour, Lyme Disease Revelation

Justin Timberlake's taking a load off after getting done touring and announcing he has Lyme disease ... and his sweatshirt says it all.

The singer just posted to his Instagram Story on Monday ... and he's rocking a gray sweatshirt that reads, "I'm not doing s*** today."

Justin's top also says ... "Mission accomplished" with a green check mark. He added some check mark emojis to his post.

The guy certainly deserves a break ... he was on a world tour performing through a medical condition he says is "relentlessly debilitating, both mentally and physically."

Justin announced his diagnosis last week after his tour ended ... though he said he wasn't looking for any sympathy.

He's been super busy for the past couple years ... dealing with an arrest in the Hamptons and a social media obsession with his bulge.