Help me please.........?

i am extremely curious to know the answer to this and a little worried. i sit cross-legged a bunch lately and i've been noticing the vein behind my left knee has become more blue and noticeable. am i overreacting or could this be from pressure and sitting like that?? also, i notice these involuntary nerve twitches in my left leg that just started happening since i've been sitting cross-legged at the computer all day. please help. i wasn't aware sitting like that could cause any problems but if it does i'd really like to know. please and thank you.