DD3 was also posterior. None of us had any idea til her head was out. She sat side ways, in an awkward position til birth, then turned the wrong way (so did the last 2, but they turned the right way during birth).

You've gotta get some faith in yourself. Thats the main thing. You've done it once, you know what to expect & you can do it again.

Two rules for a posterior birth, 1 - keep active!! Thats the most important. Posterior births tend to have a period where everything slows down because bub is in the wrong position. Moving & gravity helps baby turn/descend to keep things going. So try not to lie on the bed (my middie sent me to the toilet, thats all we needed).
2 - use a bean bag or something & try being on all fours. Takes the pressure off your back. It works! Still hurts, but not as much.

I had DD drug free. The back pain is intense, as you'd know, but you can get through it. Use pain relief, but try to remain active. Try not to do anything that will limit your movement, because that can lead to c-section.

Have faith, you know what you're doing