can heart murmur change?

Just wondering of heart murmur change over short time? Last month they heard a soft thrill over my asd repair area and lower part of heart and now on Thursday they heard a loud thrills and my doc wants me to bump my cardio appointment sooner. The only thing is that this was an allergist that I saw on Thurs due to contact allergic dermititis caused by electrodes that I had on for 21 days, he detected the loud thrills. Can this be a mistake? I had a closure of my asd when I was 9 years old now I am 31 years old and it was closed by stiches. I am having heart rate issues and blood pressure issues and that why a 21 day monitor was warrented.
Being that he was just an allergist should I still be concern? He said that's why I am having problems with walking for long period of time,excerise and heart rate/blood pressure issues. Also my pulmonary function test number was 63 he said that was not good and I do not have asthma. Is pulmonary function test reliable? My mother has very bad asthma and hers was better then mine. Should I call and bump my appoint up to Monday afternoon or Tues or can I wait until Fri,its not that long of a wait I think and he is only an allergist. Do they know something that a cardio might miss or do they know more then a cardio and should I trust him eventhough he is not a cardio?