Zach Jafarzadeh spoke out for the first time on Tuesday, claiming that the 21-year-old had abused the tranquilliser Xanax since she was 16.
He also added that things were not well in her relationship with current boyfriend Nick Gordon and this was making her unhappy.
Bobbi remains in a coma after being found face down in her bathtub three weeks ago.
She was placed on a life support machine after being found at her home in Roswell, Georgia, by her boyfriend, but has not regained consciousness since.
'It could be a possible suicide, not even just a mistake' said ex Zach.
'Something symbolic like, 'This is the way my mom died, this is the way I want to kill myself too.''
There have been varying reports about how the daughter of Whitney Houston is doing in hospital, with one family member saying that doctors 'dint have much hope for change,' while others claimed she was beginning to open her eyes.
Xanax is prescribed mainly for anxiety and panic disorders, and can also be used for anxiety brought on by depression.