"Are you bound to a wife?" (1Co 7:27). You should know whether you are still married or not. Spiritually you belong to Christ "'because of your name'" (Mk 9:41). In our society the married couple goes by the same last name. With Christ there is the "fair name by which you have been called" (Jas 2:7). If you are divorced and your "ex" has changed her last name then it is totally denying any relationship. It is a two-way street. "If we deny Him, He will also deny us" (2Ti 2:12).
The Web site www.crosswalk.com has Bible tools to exegete scripture. I used them to analyze the hypothetical statement "'unmarried' (Gk. agamois) usually means a widower." Someone wanting to constrain the discussion might want to limit "Are you unmarried? (1 Cor 7:27)" to just widowers so that divorced Christians wouldn't even be considered. According to a Greek lexicon "agamois" does indeed mean unmarried or single. "Unmarried" is used in 1 Corinthians 7:8, 7:11 and 7:27. The NIV uses "unmarried" in all cases, but in the last, the NAS uses "released" and the NKJ "loosed." Strong's Concordance defines "loosed" as a "single man, whether he has already had a wife or has not yet married." Robertson's Word Pictures of the New Testament concurs with "bachelors as well as widowers are included in "loosed." Furthermore, it states regarding "unmarried" in verse 7:8 that "it is hardly likely that Paul means only widowers and widows and means to call himself a widower." Therefore anyone using this misleading approach to precipitate a foregone conclusion is mistaken.
"If you do marry, you have not sinned" (1Co 7:28). How can anyone say that you are still married at this point so that when you remarry you commit actual adultery? All this information should leave you "fully convinced" (Ro 14:5) so that you do not feel guilty when you have to decide.