I Am Constantly Making Oxalate Kidney Stones From Both Kidneys,

I am constantly making oxalate kidney stones from both kidneys, more from one side I just had the last removed in sept. It took 5 times in one kidney and 1 time in other kidney going through the penis. The week of xmas I had pain. Continued to drink 6 bottles of water a day but now I am squeezing juice from a lemon in each bottle. I did pass about 20 different size stones with no pain since then. I am also taking Potassium Citrate, 2 pills 3x/day. No one can figure out why I get stones. When I was 27, I had my bout with stones. Every 5 years I began to get them. Since I retired 3 years ago, I now get them every 2 years now, Can you help me telling me what is possibly causing these stones. Thank You. Angelo Rosa Bellerose, NY.