Ok, so im a male 19 years old. I have a really big problem with my arm veins...

My arms look fine if my arms are straight up above my head, or if theyre crossed on my chest. However, if i let my arms hang to the side, immediately (within 2-3 seconds) a whole bunch of huge veins start bulging out of my arms, and they are really noticable. This is not painful at all, i dont even notice unless i look at my arms. This has made me completely psychotic about my arms and i have to constantly scratch my head, pretend to yawl, or do something else that will make my veins from buldging out. I am the only one i have ever seen with this condition in my life. Im not sure if it matters, but i am 6'0 and only weigh 135 lbs (yes im really skinny, but i work out so i have some muscle, but not a lot). I first started to notice these veins around 14 years old. I used to work out alot and still work out fairly regularly but not as much as i used to. Could working out my arms to much be a cause of this? Is there any way of treating it without surgury? Is the key just to gain weight to cover them up? Please give me some advise...im tired of worrying about my arms 24/7