Anxiety attacks question?

Hi, i started having what i think it is anxiety attacks in the past 2 months. Now my only concern is that it only comes when i exercise or after . It is something that happens almost everytime i have and exercise. Another concern i have is that my fingertips and toes turn blue and my hands and feet gets very very cold. I also get very dizzy, twitchy and my face turns pale. I went to the doctor and he said so far everything is fine. He ordered a stress test which is soon to be taken, late this week. Can anyone help me with this? Does it sound like anxiety attacks? Why does it happen after exertion? Thx I appreciate