Cassie Posts for First Time Since Giving Birth, Testifying Against Diddy

Cassie's back on social media after a few months away ... sharing a funny post about postpartum depression in her first social media post since giving birth.

The singer-songwriter shared a meme about the common affliction Thursday ... where a person starts and stops dancing a few times.

The caption reads, "When your old self slowly starts coming out postpartum" -- basically saying it doesn't mean she's always happy and dancing but she's certainly feeling more like herself each day. Cassie added, "Little by little lol" to the pic.

Of course, Cassie gave birth to her third child -- a baby boy in late May, shortly after she testified against her longtime partner Puffy at his federal trial.

She told the jury about his alleged abuse during the trial ... though ultimately it only resulted in his conviction on two of five charges. He was acquitted on the main charges of sex trafficking and racketeering.

Diddy's still awaiting sentencing ... and, his lawyer Marc Agnifilo spoke to us all about his priorities both in jail and after his eventual release.