Breathlessness while climbing stairs.

Respected sir, 2 months ago I had mild chest pain at different place in chest so visited cardiologist done ECG 2D ECho TMT all are normal..done almost 5 ECG later all are normal, 10month ago did same ECG 2DEcho TMT all are normal.. But now from last month i feel little breathlessness and chest tightness when climb stairs fast..when walking half hour no feel tightness but little breathlessness it's not discomfort me but my attention goes there.. It's all started after so many test negative so I visited pschytarist and he prescribed some medicine sertaline 50mg after starting medicine i unable to sleep 2-3 night later and started sever stomach upset and burning feeling in center of chest...so stopped medicine but problem last 8 days after that this breathlessness and chest tightness at center started.. Please let me know is this heart blockage problem I m 34 Male and have high cholesterol 1 year ago later reduced to normal..in stress since 1 year..what should I do