Rash at 30 weeks

I got a rash on my upper thigh, I usually get it on my arm and hand but no where near as much as I have on my leg right now. Everytime i phone my doctors about it they just tell me to wait for a call and then tell me not to worry about coming in. I have discussed it with my midwife but whenever I see her, it disappears. And I'm not seeing her for another 2 weeks. Any guesses on what it might be?

It's not itchy or painful to touch but it is slightly raised