pubic symphysis dysfunction

Anyone have advice on birthing positions or labor positions? My pelvis currently grinds together every time I cough and I'm 34 weeks. Starting to get nervous at how this birth is going to go. It hurts to separate my knees and do stairs. Walking is getting more difficult as well. I didn't have this with my first two, just want to know what I'm getting into this time around delivery wise. My OB has brushed it off so far. Thanks!