S.T.
Don't freak out, and I don't want to scare you, but ask the doc about PUPPP. It stands for something long and scientific like "polyuritic polyps and postules of pregnancy"...I think that was what they called it. I had it with my first baby and it SUCKED!!!
It started on my belly, much like you described, like a chigger bite. Anything tight or hot seemed to make it spread and get inflammed. It itched day and night and spread pretty much everywhere but my face. It is miserable and the only "cure" is to have the baby and it will go away shortly after the hormones die down. Again, not sure if this is what you have, and I hope it is not.
If it is PUPPP, then they will give you hydrocortisone creams, which didn't help that much, and Aveno bath which will help as long as you can stay in the tub. Sorry, there's not much bright side.
The only positive if you think it is positive is that I had it with my daughter and not my son. So perhaps your body is incubating a little boy and your skin is reacting to the different hormone levels.