The issue of apostasy is a complicated one and the cases are to be individually treated by a judge. In brief, there is no repentance from a person who is born in the faith and who then becomes a confirmed apostate.
As for one who converts from another religion and then turns away from Islam and later repents his repentance is accepted.
But in your case, since you didn't know and are regretting it, your repentance is definitely accepted. Do not make such grave and baseless decision when you are upset and or mad. That stops you from thinking correctly and you end up saying such things.
Ask An Alim Team.