To be a real heretic you must, in fact, have been an adherent of the beliefs about which you are commiting heresy. If you didn't believe that stuff in the first place, you are not an heretic.
A church that breaks away is a schismatic church. You do not belong to a schismatic church. Your church, while nominally Christian and whose doctrines do derive from Christian dogma, holds and promulgates heretical views i.e. doctrines different from those of the Church. Therefore, ergo, and thus- you are a heretic.