If the FBI contacts you, of course you’re going to be freaking out! Try to remain calm and poised. You don’t need to give them any more reason to be suspicious of you.
What you should do is get a lawyer. Let the FBI know you do not want to answer any of their questions without consulting your lawyer first or without having your lawyer present. That is your right. The FBI will not be allowed to question you any further.
You may also deny FBI if they want to search you, your belongings, and/or your property. Unless they have a warrant, they will have to concede to your request. However, we do caution that under certain circumstances, the FBI may be allowed to scan and search the small vicinity or you under probable cause.