What Causes Welts On The Abdomen With Severe Itching?

I ve been to a dermatologist and they put me on a steroid for 6 days and some other antibiotics but now I am still itching on my calves ankles and now I get welts on my lower stomach that itch every so often. I want to call them and ask what s going on but I ve been to see them twice and it doesn t seem like they really know what s going on with me.