what dress to wear for second wedding

I just came back from the doctor and she told me that I am 3 centimeters dilated and 80% effaced.. like what does this mean?? I'm still at work at the daycare so I'm getting nervous lol I don't think I have been feeling contractions just back pain after my first internal exam.. I'm 37 weeks and 1 day. What should I expect?? what dress to wear for second wedding