Talk it Out
Your hands may touch the other's when papers are exchanged. You may lean a little too closely while discussing a project. Do these gestures suggest deeper interest? With an office romance, you have to be very sure that the interest is mutual. As embarrassing as it may get potentially, you just have to talk it out with each other.
Maintain Formality and Distance
This can help you maintain your professionalism. Also, you won't cross the fine line between your work and private life, so that you two can maintain your colleague status more easily. Believe it or not, it will actually help keep that romantic feeling going between the two of you.
Be conscious not to increase the amount of contact with your partner at work. Don't lunch together more often than you did, or leave together after work.
Check your company's policy on dating a co-worker. If your boss is unhappy, you may want to ask for a change of workstations to minimize contact with each other on an official basis.
This is always hard to do because you still have to face each other everyday, work together on projects or worse, go on business trips together.