I've been having some troubles as well - mostly because I tried to move something too heavy and my mid-back is in spasm. In fact, I was in so much pain the other night, I put DD into the cosleeper for part of the night until I felt better. She did okay, but was restless. I am going to continue putting her in the cosleeper at least until her first nursing of the night.
A few other things that may help -
In the short- to medium-term:
1. For those with carpal tunnel, wearing a brace at night really helps.
2. If you're not adverse to meds, some advil at night will help muscle spams and other problems. When I had runner's knee years back, it really got me back on track. I used it last night as well as having DH rub an ointment on my back and just one night of treatment really helped get me back on track, so to speak.
3. Moist heat for any spams or sore areas on the back or shoulders- 10 minutes every hour is ideal, but who has that kind of time? Either a moist heat pad or letting the shower run over the area helps. Follow up with some light stretches for the back and shoulders.
4. Supta Baddha Konasana (reclining goddess) with a bolster under your back is awesome for moms. see http://www.yogajournal.com/poses/663_1.cfm
5. acupuncture. i've found "medical" acupuncture to be useful in relieving muscle spasms.
In the long-term:
2. I haven't done this yet, but am looking into Heller Work (http://www.hellerwork.com/)
. Other moms I know say that it realy helped them along with yoga.
3. Chiropractors do help, but only if they provide you with tools for the long-term, especially exercises to do.
4. Include foods with natural anti-flammatory properties in your diet such as ginger and EFAs, and bromelain.
And if you have ongoing back problems, check out any book by Dr. Sarno. Really enlightening!