Welcome to HCM,
first of all now after words do not take steroid
therapy empirically as it is temporary helping in this case.
first we have to diagnose it then proper plan of treatment will decided. as you mention that some of tests are negative. so i thing it is a case of auto immune disorder.
Do ANA test. i suspect it will be positive.
reply with ANA result.
mo: +91 9726491149
have a good health