Varicose veins can cause cramping alone. If they are increasing in size or you are having increased cramping its best to speak with a doctor, you may need to have surgery to remove them and relieve the pain.
Cramps are commonly associated with varicose veins since these are enlarged veins that do not carry blood properly. Your cramps could be symptoms of restless leg syndrome, which is also common for people with varicose veins. It would be best to see a doctor asap to rule out more serious conditions.
Varicose veins in legs are very common in old people mostly. At the same time pregnancy and standing up for a long period of time make this problem worse. The cause is pathological distention of the veins, due to anomalies of the valves. You should go to the doctor for further information as there is a possibility fo thrombosis.
Some of the reasons could be fatigue that comes from standing for long periods of time. If you're job requires standing and you've done that job for years, that could likely be the reason. Other reasons could be heredity and/or poor circulation.
Try eating bananas as an easy way to increase your potassium intake. The lack of potassium in your diet could be causing the painful leg cramps. Also, increase circulation by walking, jogging, or running more often. The increased circulation should help to alleviate both the leg cramps and varicose veins.
You should see a doctor to discover whether you have poor circulation -- peripheral vascular disease. Meanwhile, try taking over-the-counter magnesium supplements, which help a tremendous amount with cramping.