I am so sorry for yuor situation.  If you were never legally divorced from your first husband then yes, you were not legally married to your second hisband.  I would seek legal help not only about remarriage but about making sure that your other documentation  - such as a Will or deeds - are also valid at this point in time and what you need to do regarding them.  Also check beneficiary designation forms (re-designate each other on those) and joint accounts.  I would try and obtain a copy of his death certificate.  Good luck.