Short answer. Yes, you can still be charged. Believing your first marriage was void is not the same as having it declared void. The Family Code requires a judicial declaration of absolute nullity of a previous marriage before a person may remarry, and remarrying without one exposes you to a bigamy charge.
What the law says
The penalty of prision mayor shall be imposed upon any person who shall contract a second or subsequent marriage before the former marriage has been legally dissolved, or before the absent spouse has been declared presumptively dead by means of a judgment rendered in the proper proceedings.
Revised Penal Code, Article 349 — Bigamy: Second Marriage. Read the full provision →
Why your own belief is not the test
The article keys on a fact, not on a state of mind: whether the former marriage "has been legally dissolved" at the moment you contracted the second one. Notice how the provision handles the parallel situation of a missing spouse — it does not ask whether you sincerely thought your spouse was dead. It demands a judgment rendered in the proper proceedings declaring the absent spouse presumptively dead. The same logic runs through the Family Code, which requires a judicial declaration of absolute nullity of a previous marriage before a party may remarry. In both cases the law wants a court's determination on record before a second marriage is celebrated, not a private conclusion reached at home.
Getting the declaration afterwards
A very common situation is this: the second marriage happens first, the petition to annul or declare void the first marriage is filed later, sometimes only after the complaint is made. Anyone in that position should understand that a later declaration does not automatically undo the exposure, because the offence looks at the state of things on the date the second marriage was contracted. Nor is a barangay agreement, a church annulment, a long separation, an affidavit of separation or a spouse's consent a legal dissolution. Only a court judgment, or the death of the first spouse, ends a marriage for this purpose.
What the prosecution actually has to prove
The elements are concrete and documentary: a first marriage that was not yet legally dissolved, a second or subsequent marriage contracted while that was so, and — since this is a felony — that you acted freely and knowingly rather than under a genuine mistake of fact that negates criminal intent. In practice the case turns on marriage certificates from the civil registry and on the dates in the court records. The penalty is prision mayor. Consequences beyond the criminal case often matter just as much: property relations, legitimacy and support for children, immigration status and employment can all be affected.
If a complaint has already been filed
Gather the primary documents before anything else — certified copies of both marriage certificates, any petition or decision touching the first marriage, and proof of the dates. Do not sign affidavits prepared by the complainant's side, and do not assume an amicable settlement disposes of a criminal charge; bigamy is prosecuted as an offence against the State, not as a private grievance. Nothing here predicts how any particular case will end, and it is general information rather than advice. Whether a defence exists on your facts is something to take up with counsel who can read the actual records.