I've been though a different set of injury hell, but you definately want to nip problems in the bud. I'm seeing 2 here.
1- Core strength issues. If you feel like your gut is hanging out and your lower back is hurting, you're begging for SI joint trouble. I've got it, wouldn't wish it on my worst enemy. Get thee to the gym and work on the abs and pelvic floor muscles. Yoga and Pilates are super for this, but so is just hitting the floor and running through a good set of ab exercises. Crunches will fix a lot, done daily. Get some help and find out if you're doing them right. You can roll out of bed, get on the floor, and do 150 good crunchies in about four minutes.

2- If the refit fixed one problem but started another, go back. You may just need a tweaking. Better to check now than hurt. Neck pain can come up out of shoulder problems, and that can be from the fitting.

Lizzy