Can An Arm Cast Cause Vein Discomfort, Breathlessness With Headaches?

Age 17, Height 5-8,Weight 160. i have a cast on my left arm that passes over my elbow. its been 3 weeks and only recently have i been breathless and my cast and arm feels weird in the vein area. i have had constant headaches and i just wanted to know if this means that i need to take my cast off and get a new custom 1.