Non Prescription drugs that can help me overcome anxiety?

My anxiety has been really really terrible lately. I don't know where it comes from or why I have it but it has gotten to the fact where I can't even function like myself anymore. I am going on a vacation on Thursday. I am already feeling anxious about the plane, we're going to Europe so its a long ride. I am afraid that I will have an anxiety attack while on the plane and I don't know what I will do. I need something that I can take that will help to calm me. I am tempted to take a xanex but I am afraid to do that too. Any suggestions? Thank you so much.