A marriage may be annulled for any of the following causes, existing at the time of the marriage:
(1) That the party in whose behalf it is sought to have the marriage annulled was eighteen years of age or over but below twenty-one, and the marriage was solemnized without the consent of the parents, guardian or person having substitute parental authority over the party, in that order, unless after attaining the age of twenty-one, such party freely cohabited with the other and both lived together as husband and wife;
(2) That either party was of unsound mind, unless such party after coming to reason, freely cohabited with the other as husband and wife;
(3) That the consent of either party was obtained by fraud, unless such party afterwards, with full knowledge of the facts constituting the fraud, freely cohabited with the other as husband and wife;
(4) That the consent of either party was obtained by force, intimidation or undue influence, unless the same having disappeared or ceased, such party thereafter freely cohabited with the other as husband and wife;
(5) That either party was physically incapable of consummating the marriage with the other, and such incapacity continues and appears to be incurable; or
(6) That either party was afflicted with a sexually-transmissible disease found to be serious and appears to be incurable
almost all of this grounds prescribes after 5 after the marriage.
she can file a petition to get the child if she wants, she can file concubinage, on the other hand you can file adultery, it does not matter who commit the crime first. You can initiate the filing of annulment but i doubt you have a solid ground for annulment and it takes a long time and there is a chance that the petition may be dismissed.