It would be best to hire a lawyer, provide the lawyer with a copy of everything you submitted to USCIS and the letter you were given that day. Only then can an accurate response be given and you'll be able to ask additional follow up questions.
There is no way to determine whether you have a possible problem or whether this was typical procedure. You will have to be patient and wait for the result. If you receive an Intent to Deny you will have a short period of time to respond. I suggest you contact an experienced immigration attorney to assist you with the response.
It seems that the Service may need to do further review. Even in situations where the marriage was clearly entered into in good faith, the officers may not say anything other than "We'll send the decision in the mail." Give them time to do what they need to do. At the same time, seeking help from an immmigratoin lawyer would be your best move if the adjudication time is getting longer.
Madrid Crost Law Group - (888) 466-4478; e-mail: email@example.com; skype: usvisalaw 10 S. La Salle Street, Suite 3320, Chicago, IL 60603 Please consult with a licensed immigration professional to provide you with a thorough legal advice. This response is not a substitute for specific legal advice and it should not be construed to create an attorney-client relationship. Please help stop notario fraud. Please visit and share this site: www.stopnotariofraud.org.
Since you are trying to do this yourself without an attorney, the result will be more likely to not be positive. Obviously something in your application caused them to become suspicious, an experienced attorney would have most likely observed this and save you a lot of stress, time, and money.
Legal disclaimer: The statement above is general in nature, as not all the facts are known. You should retain an attorney to review all the facts specific to your case in order to receive advise specific to your case. The statement above does not create an attorney/client relationship.