Slight Pain and Sinking Feel in Chest.

Hi.. I'm 33 years male with six feet height and 110kg weight. For last 5 to 6 months I sometimes feel a slight pain in chest left side and sometimes Sinking Feel as if someone is pulling my heart down. Feeling comes on its own without any increases physical activity and goes away on its own in few minutes. I visited doctor also. He got my ECG and Chest x-ray.. Both are normal. Sugar level and Cholesterol also normal. Then HS-Trop-i test came less than 1.5 also. But vitamin D came out 4.5 (deficiency) Doctor told me this pain should not be cardiac related and I should not worry. But still I'm not clear why this pain occurs sometimes. And thought of it puts me in anxiety. I m a non drinker and non smoker. No history of Diabetes or Cardiac Disease in my Family also. Plz give some advice. Any feedback would be much appreciated..!!