Why do I always get rashes on my thigh when I shave my legs?

I've shaved my legs twice now, and the first time I did it, there were rashes all over my thigh, so I had to go to the doctor and get some cream. The second I did it, on Thursday night, I have now got all these rashes on my thigh again. It's only on my thigh and not on my legs. What is it? Why does it always happen? How do I treat it??