How to sleep on your side using pillows between your legs and not hurt your calves?

If I understand...: You mean when you have a pillow between your thighs it feels good, but then your knees and calves feel unsupported after awhile? If so, try using two pillows, one for top and one for bottom. Or a king size pillow, which is much longer (a queen size might do, if you are petite). Some people use mushy body pillows instead, but this depends on how much room there is to spare in your bed! Be well : )