It is difficult to diagnose any illness, but BPD presents special challenges as this article details because of overlapping symptoms.
Borderline Personality Disorder Difficult To Diagnose | Psych Central News

If it can be proven you are a suicide risk or a threat to your children then removal of the children is possible. A diagnosis without substantiating a risk or threat is unlikely to stand up in court. Any actions you take could be used as justification by the state in any proceedings. If it has got to this stage where you fear losing the children, a lawyer specializing in this are might save you a lot of grief and heartache.