I'm just over 34 weeks now and been suffering with ridiculous back pain, literally at times I feel like my muscles are tearing it's horrible. I tried a wheat bag thingy which you put in the microwave which worked really well but I needed something which I could walk around with. I went into boots etc but could to find anything. And then I came across this thing called 'Hotties' on amazon it's about £20 including postage and worth every penny! I at last can walk around virtually pain free. It's basically like a huge belt which ties around you with a pocket in it which holds the microwave pouch. It's a simply design but very effective and helping me enormously. One thing I'm quite petite and fits around my tummy, it has an extendable bit but not too sure if it would fit those who are a bit larger.
Thought I would recommend it as it's really helped me, and before anyone asks no I don't work for the company! Just a fab find to help with the last few weeks which I wanted to share
I won't post a link just in case, but I think if you put in the search box 'hotties soothing back wrap' it should bring it up!