Are we bigamist if we are still married to each other in our country even if we got a divorce here?

Generally, the USCIS will consider a divorce to be valid if the divorce was lawful in the place where it occurred. If you are considering sponsoring a spouse for immigration benefits, there really is no substitute for consulting with an immigration attorney who, after learning all of the relevant information, including divorce details, could advise about eligibilities, options and strategies to attain your goals, and who then could offer legal representation in the often complex application process.