What Causes The Severe Outbreak Of Hives?

I have been breaking out in hives for about 2 months now, My doctor recently prescribed me steroid type pills to clear this up. I have finished the 10 day treatment on Thursday and noticed that the hives were returning as of yesterday (Sunday). I have an appointment to have blood work done tomorrow. I also wanted to mention that I have been having a terrible pain that feels like it begins just below my sternum and then radiates like a tightening horrible pain across my entire chest area. I also feel like there is some type of blockage in my throat where my neck meets my chest (I don't know what it is called). When i swallow or talk I feel it and it is uncomfortable, I sometimes feel pain in my jaw as well. Please help me :( ??