Former Miss USA Cheslie Kryst was suffering from depression before taking her own life -- this according to her mother ... who's speaking out in the wake of her daughter's death.
April Simpkins says ... "I have never known a pain as deep as this. I am forever changed," adding the family had confirmed Cheslie died by suicide last week in NYC.
She continues, "While it may be hard to believe, it’s true. Cheslie led both a public and a private life. In her private life, she was dealing with high-functioning depression which she hid from everyone -- including me, her closest confidant -- until very shortly before her death."
April goes on to say Cheslie's life, despite being short, was full of beautiful memories ... and, naturally, she'll be missed by her loved ones.
Her mother also said, "Cheslie -- to the world, you were a ball of sunshine wrapped in smiles. We talked, FaceTimed or texted one another all day, every day. You were more than a daughter -- you were my very best friend. Talking with you was one of the best parts of my day. Your smile and laugh were infectious."
She finished with, "I love you baby girl with all my heart. I miss you desperately. I know one day we’ll be together again. Until then, rest easy and in peace."
Rather than ask for flowers, her family is asking for donations to Dress for Success -- an org Cheslie held in high regard. Her mom also posted a number for the National Suicide Hotline ... encouraging anyone with suicidal thoughts to seek help.
As we reported ... Cheslie died Sunday when she jumped from her NYC apartment building. She was just 30 years old.