If the USCIS determines that there was marriage fraud, they can not only deny the naturalization but can also place you into removal (deportation ) proceedings. Under the circumstances, I recommend that you consult with an experienced immigration attorney.
Did the interviewer say something to you to lead you to assume that the validity of your marriage is the reason for the delay of your naturalization application? There are many reasons why a naturalization application is not approved immediately. One common reason is the the background check has not cleared. There are many thousand naturalization applications that are pending because of the background check.
If you have reasons to think that the government may question whether the marriage was bona fide, you can start collecting evidence to show that the marriage was bona fide. Such evidence may include documents showing a commingling of finances such as joint income tax returns, joint bank accounts, joint credit cards, pictures of activities done together, phone bills showing calls between the residences. People who live together as husband and wife have many other ways to show the existence of their relationship.
You can review you options with an attorney.