Thanks for your question on Health Care Magic.
I can understand your situation and problem.
Yes, you should definitely
consult doctor and rule out cardiac and Pulmonary causes.
Since you are out of shape (
obese) and having breathlessness and left sided
neck pain, cardiac cause must be rule out first.
So get done ecg and 2d echo.
If both are normal then no need to worry for heart diseases.
Get done PFT (Pulmonary Function Test) to rule out
bronchitis (lung related causes).
Loose weight and follow healthy lifestyle.
Better to first diagnose yourself and then start appropriate treatment.
Hope I have solved your query.
Wish you good health. Thanks.