You are most probably suffering from anginal pains which means blood supply to your heart is decreased. Smoking can accelerate atherosclerosis of blood vessels and cause cardiac problems at early age.
Next Steps
Get ECG and Echocardiography of heart done after consultation with physician or cardiologist. Dont delay this.
Health Tips
1.Stop smoking. 2. Take healthy diet low in oil and spices/ salt . 3. Regular exercises.4. Adequate sleep.