Welcome to HCM
We understand your concens
I went through your problem description. I sincerely suggest you not to worry too much. Your doctor had already opined that your heart is fine. He cannot advice without having been confirmed himself. Therefore please stop worrying. The breathlessness could be associated with either your obesity or with the anxiety
You need to walk at least 1 hour in order to reduce your weight. Diet alone may not work without stringent exercises. Aerobic exercises
are known for weight reduction. You learn some form of dancing. You are just 23. Young enough to do all these. Laugh at your destiny and don't cry at your current position. Anxiety about weight will increase the weight, actually. Be happy and watch the weight being reduced.
Hope this clears your doubts. Available for further clarifications.