Rips NFL In Emotional Video

"My NFL brothers continue to die and nobody's doing a goddamn thing about it."

Ex-NFL quarterback Ryan Leaf fought back tears in an emotional video in which he accuses the league of turning its back on players with mental health issues ... and lamenting, "I don't know what the f**k to do anymore."

Leaf posted the video AFTER after news broke about the death of ex-NFL star wide receiver Vincent Jackson, who was found by himself in a hotel where he'd been living in Florida. We don't know if Leaf is referencing Jackson in the video, but it sure seems like it.

"The NFL just doesn't f**king care," Leaf said ... "They don't care. They'll write condolences letters and s**t like that but if they were…