بسم الله الرحمن الرحيم
(Fatwa: 28/34/L=01/1435)
If the husband is missing in a way that it is not even known whether he is dead or alive then the woman should file her case in local Shariah Panchayat. After investigating the case, if the Panchayat revokes the nikah as per the provisions mentioned in ‘Al-Heela Al-Jajizah’ then the woman shall be eligible to marry somewhere else after passing her iddah. You married second time without revoking your nikah, it was not valid. You should separate yourself immediately and you must not marry anywhere else until your nikah is not revoked as per the Shariah method and your iddah is not over.
Allah knows Best!
Darul Ifta,
Darul Uloom Deoband