You can review the naturalization requirements to see whether you can apply now. The Guide to Naturalization has the information for most common scenarios. The Guide is free at http://www.uscis.gov/natzguide .
You can also review the instructions to Form N-400. The forms and instructions are free at www.uscis.gov .
Applying because you are married to a US citizen requires that you are still married to and living in marital union with that US citizen until at least after the date of taking your oath of naturalization.
You can also review your facts with an attorney to see if there are any potential problems.
A person who obtained his/her permanent residence through a marriage to a US citizen may file for the citizenship after 2 years and 9 month after becoming a permanent resident. However, under current USCIS interpretation you need to stay married to your spouse until the time of the oath. In addition to a three year permanent residence requirements you need to meet other criteria, such as physical presence and good moral character, pass a language and US government and history knowledge tests.
Please contact an experienced immigration attorney to discuss possible issues with your particular case. Immigration law is a federal law and a lawyer licensed in any state can assist you in your case. The responses and information are intended to be general and should not be relied upon for any specific situation. Best of Luck!
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