https://www.mayoclinic.org/diseases-conditions/mitral-valve-disease/symptoms-causes/syc-20355107
Hello @nanthitha, it looks like you are new here, welcome to Mayo Connect.
I posted a Mayo Clinic article for you to read that you may find interesting.
I have always found learning as much as you can about a condition you have is helpful. Sometimes though, we can may ourselves fearful and stressed if we overthink things. Anxiety can cause physical symptoms like you describe as well as a heart condition. It's stressful to fear you have something and nobody seems to be listening. It sounds like your second opinion is trying to work with you.
There is no one who knows you better than you!
I was diagnosed with a mitral valve prolapse when I was 22 years old. It caused a few little issues along the way like rhythm disorders such as PVCs and tachycardia. I also had to pre-med with an antibiotic before teeth cleanings. Fast forward many years, and I learned I did not have a mitral valve problem at all...it was due to hypertrophic obstructive cardiomyopathy, or HCOM. I'm not suggesting you have this at all! I am saying listen to your body, and if you still feel, even after being reassured, there is something wrong, a third opinion is not unreasonable. I think any of us gets a little nervous when we think there is something wrong with our heart. It's an important part of us!
Aside from what you are experiencing, are you active? Do you exercise regularly and eat healthy? Do you have a favorite hobby or pastime that you enjoy?