Make a plan for your lunch hour the night before or even better - plan them out a week in advance. Schedule in phone calls to vendors, errands, short shopping trips, work on your "to-do lists", reply/send emails to vendors, wedding attendants or family members.
Bring your lunch to work. This will save you at least 20 minutes from standing in line to buy your lunch. And, an extra benefit - it will save you money too!
Delegate as much as you can! You've got TWO full-time jobs now, so enlist the help of everyone you can.
Keep the "wedding planning updates" with co-workers to a minimum. You don't want your manager to think you're spending more time talking about the wedding and less time working.
Save up those vacation days. You'll need them for your honeymoon and a few days before the wedding.
If you need a vendor to call you back at work, ask them to return your call at a designated time, like between 1:00-2:00pm. This will help you better separate work and wedding planning.
Use email as much as possible. This greatly reduces phone tag AND reduces the chance that your caterer will call you about menu choices when your boss is in your office.
When work gets busy and wedding planning kicks into high gear, your biggest defense is to stay organized. Find a system that works for you (index cards, notebooks, software program, etc) and STICK WITH IT!
If you begin to fall behind in your work load, try coming into work an hour earlier (before most people arrive). Many times you can accomplish more in one hour of "quiet time" than you can all day.