I wouldn't discount the hypnobabies work you did just yet, though, because pre-labor is often responsive to a changing physical or mental state. By calming yourself you reduced your catacholamins (or however that's spelled) which in turn stopped the contracting. It's weird but known that pain can cause labor or at least contractions as well as the other way around. So by stopping your pain and calming your mind you could have stopped them. (I learned about the effect of pain last time I was pregnant, I think I learned it from the multiples book I was reading)
If you experience other types of pain like the incidental kitchen burn or whatever, use hypnosis on that. Practice on whatever rail pain you encounter and master your reaction/interpretation of the experience. Even banish itches like the typical mosquito bite.
Also, I agree about your back. And I feel sympathetic for both of you right now. He just wants a happy birth for you and everybody, it seems to me. Remind him and yourself that all births are different. I'm glad you will be seeing a chiro. I wonder if a back board that you could hang upside down on would help? My fifth birth was painful and hard work for half an hour (posterior) after a breezy simple 4th birth, which shocked my husband and made him feel like birth was a hard experience. But the last one was such a thrill he's really experienced a changed perspective on the process. Sometimes it's hard, sometimes it's easy. I never used a swopper in pregnancy before, maybe that made a big difference. It wasn't pain free but really easy, nothing to make me curse or him to pull his hair out - and quick.
I had back trouble a lot for years. So bad some days I could barely stand to put one foot in front of another or even roll over in my bed. I got rid of the problem several ways. One, I started keeping my back hyrdaulic systems more hydrated with sodium citrate, two, I started grounding my bed (massive difference instantly) - research the power of grounding, it's real and reduces inflammation, and three I got rid of the last of my pains with a swopper chair. The swopper is so great! Its' perfect for strengthening the core, which you need to keep your back aligned. My husband has had lower back pain for a long time. After sitting on my swopper he had to get one of his own and hasn't had any more pain since. So now I might sometimes feel a little leg/back pain for a few minutes at a time once every couple of weeks - generally due to bad posture combined with dehydration but that's about it. (actually I also started taking pregnenolone supplements which cut down on inflammation and a few other useful natural nutrients that keep up the metabolism.) All those things happened between those two babies that made such a huge impact on my back pain and general quality of life.
I've been sharing your situation with my husband and my husband really wants you to read book Your Body's Many Cries for Water F. Batmanghelidj, M.D. because it made such a huge impact for him and others he has shared it with. It covers the causes of back pain relating to dehydration among other things.