Duphaston during 2nd Month and rashes at the back. Is it allergic?

I was given Duphaston during my 2nd Month. After taking it for 1 month, I had rashes in my back. When I told the dr. she asked me to stop it and prescribed Folliderm 10mg to take for 50 days. I still have those rashes at my back and is itching. WHy was Duphaston given to me? Is it allergic to me? Now It is 4 months complete and going to 17th week of pregnancy. I am taking foliwise and folloderm everyday. I was iven a TT injection last week and it is ver painful aswell. Please let me know, if my dr. is prescribing the right medicines.