What is the reason for my symptoms after bypass surgery and please suggest the line of treatment.?

I had a major heart attack in the year 2000 and angioplasty with non medicated stent was performed on LAD. Again I had a problem of angina, so undergone coronary artery bypass graft one and half year years ago and I am now aged about 46
years. My three arteries were blocked (includind left main near stent) which were by-passed by taking memory arteries from my chest and one artery from my left hand.My total graftings were five. After than from begining I was complaining about shortness of breath and chest discomfort. My sixth month stress test and one year stress ECO was normal than also I am not comfortable. Now I started
getting heaviness in the chest during initial walk.I can climb two floors of staire cases. But after doing such activity I am getting chest discomfort witout angina and it remains for four to five Hrs. What is the reason for this symptoms ? Due to this I am not able to concentrate on my daily activities. Shall I
again go for sixth month stress test or angiography ? My medicines are Dilzem-30
(1-1), Ecosprine-150 (1), Betalog-25(1/2), Zyrova-5(1). I am doing regular yoga
and pranayam since last six months and evening walk for 30 Minutes. Initially
during walking I am not getting comfort feeling.My BP is 125/80 mm Hg.I am non
smoker.I do not have diabities. I am not over weight. Is it require to increase
medicine to over come my symptoms ? Please answer me.

I’m not a doctor so I don’t give medical advice. For medical questions I usually go to WebMD http://www.webMD.com they have a symptom checker on the right hand side of the main page or the Mayo Clinic help site http://www.mayoclinic.com/ they have on-line specialists to answer medical questions. Thanks