Hi Hakuna.
Welcome to our Mattress Forum! 
You’re not alone in finding more support and comfort on the couch and you’re right on track having someone check your alignment. Please do keep us updated on that front!
It’s possible that you’ve trained your body to sleep in a funky position which is why you’re experiencing some pain on a mattress. However, you shouldn’t be experiencing excruciating or lasting pain after you’ve been up for a while. It’s also possible that your body is currently requiring different support since your body is different than pre-kids. So, it’s normal to assume your pre-baby mattress isn’t gonna quite do the job.
I have the same issue. My mattress pre-baby was fine. Now, I find myself with sore hips and tossing and turning. I need more support in my lumbar and hips than I did before.
It sounds like the “zoning” from couches and futons is what your body likes right now. We’ve had couch sleepers ask for help in the forum before so this convo and this one may or may not have insights for you.
Personally, I think you may have more success on a pillow top which feels/is created more like a couch with similar materials or potentially a 7 zoned mattress could do the trick.
NikkiTMU