What Causes Itching Splotchy Red Spots On Hands And Legs?

I have itching splotchy red spots on my legs, arms, hands, back, and feet. They come and go. I thought it was an allergic reaction and have been taking benadryl and went to the doctor and got a steroid injection. It still didn't go away. After thinking about it the rash started the day after me and my boyfriend had a bit of an oops. Could I be pregnant and my body rejecting it?