Abnormal heart beats. Exercise routine.

I have been noticing change in Heart beats while exercising. I am a regular exerciser. But last month I have been noticing change in heart beats though I am only doing a little bit of exercise heart rate shoots up as high as 170 up and sometime it goes down like 57 69 even when exercising. Why this is happening I don't know. I have stopped exercising. BP is normal. ECG and ECHO is normal. But I want to resume my cardio exercising. also I love to take new exercise challenges. I feel my pulses in various areas . some times palpitation happens. But no serious issues. My blood test counts lower erythosites, esr is high. slight lower Hb, creatinine is at 1.19 Can Any experienced Doctor explain Why My heart rate falls in normal range though but it keeps fluctuating like in a normal 60 sec beats If beats per 1 sec counts, it varries from 69 to 110 OR 47 to 99 So my avg 1 min heart beat falls in normal range but Deviation is greater. Also Want to know How to resume my exercise routine.