First off, sorry you are having to deal with this, I had roaming hives for 3 months and I know how miserable they can be!
Turns out I had a bladder infection and when I took the medication the doctor gave me, most of it went away. But I still got traveling hives in random places on my body. I went to an allergist and he said he had no idea why they started, but to get rid of it, we needed to get a heavy dose of anti-histamines in my body. So he prescribed 2 Zyrtec and 3 Zantac a day.
The Zyrtec is a non-drowsy Benadryl and it's supposed to be taken once a day, but with all the histamine in your system, you need a stronger dose. The Zantac seems weird because it's an acid-reducer, but my allergist said that there is a secondary histamine blocker in it that the Zyrtec doesn't have.
I know it sounds strange, but I did this and I saw progess within a week and was hive free within a week or two after that and haven't had them since. Hope this helps and you get some relief soon!