10 weeks pregnant and have a blotchy rash on my torso and back, no other symp. called my ob and got no call back, i tried benadryl for 3 days because it don my approved med list. none helped, i went to urgent care today they wouldn't give me anything?

I would see your regular doc. It may or may not be allergic, in which case antihistamines would be no help. If it is a feature of an otherwise unrecognized viral infection it may be a problem for baby. If it is just local reaction to something than you came in contact with, it should fade over time.

Try contacting OB again. If no reply see a Dermatologist and a different OB