For years now, my veins have changed. ive been told theyre squiggly and full of valves. i didnt have this issue as a young adult. what causes this?

All veins have valve: (s). Poorly functioning vein valves can lead to varicose veins. Other contributing factors would be obsity, lacking of exercise or genetic factors.

Veins: Particularly leg veins will dilate and be more noticeable as we age. This can be due to aging, and veins weaken and become less elastic. Over time the veins a bigger secondary to venous dilation and typically change in body mass as we get older.