You can call your card's customer service and let them know of your suspicions. You can even request a new card number if you think it's worthwhile (I don't think a fraudulent charge is required for this -- you could have simply lost your card). However, it's important to be clear on what is fraudulent.
You provided your credit card number willingly, so that transaction would only be fraudulent if and when the site charges your card and fails to provide the item as agreed. (I take it they don't have an option to cancel your order.) You haven't clearly stated whether the expected charge for the purchase itself is showing in your card activity (and you're just watching for additional charges). A legitimate site typically charges your card when they ship the order. So the outcome will depend on how carefully they pretend to be legitimate.
As for other unexplained charges from this site or its shady associates (beyond what you authorized for this purchase), which are what you could have avoided by using a virtual number, those would be prima facie fraudulent and could be reported as such if and when they occur.