Weddings are not off topic at all. Reassure yourself that weddings can be very stressful and anxiety heightened for EVERYONE even if they don't have anxiety/panic disorder. Also, try your best to recognize your geniune excitement jitters seperately from your anxiety, so you can also enjoy the fun moments of planning too.
My father gave me the best advice for my wedding I think. He said, "Do what you can to plan it how you want in the days leading up to it, BUT from your rehearsal on through the wedding day, don't think about ANY of your plans. So once the rehearsal starts, the planning is DONE & its yor time to enjoy all your work. Just remember that no day goes off perfectly so just go with whatever happens, the end result is you're still with the one your love & if you can do go with the flow, you'll remember that day fondly no matter what".
Our day did not go "perfectly" according to the plans, but I honestly can't remember what was different from my plans, I loved every minute of it. Good Luck & enjoy YOUR day!
