I have heard that it is quite common for doctors to misdiagnose schizophrenics with bipolar and bipolars with schizophrenia. It sounds like you might have post traumatic stress disorder, which is similar in symptoms to schizophrenia and bipolar disorder. Talk to your psychiatrist about your concerns.
It certainly is possible to be misdiagnosed. If you feel well and don't take any meds, you're probably safe. Having said that, it would mean you have ovecome your past issues and don't have PTSD or something else going on from suffering such horrible abuse. Just to play it safe, I would meet with a psychiatrist and explain your situation and see what he/she thinks. You don't want to be off medication and start having suicidal thoughts that you could act on. I think the typical onset age of Bipolar is in the mid twenties. But there are a lot of other things that could have been going on so I wouldn't shut the door without speaking to a doctor first-for your own safety and peace of mind.
Best of Luck
Erin