Hi, The cause of foamy urine may be some times very much normal, particularly, if you have a strong stream of urine with a full bladder. However, this may be an indication of some presence of proteins in the urine, usually as a result of some kidney disease. As you have an history of kidney stones, this may be one of the reasons for you to have protein in the urine. How are you sure, that you have passed all the stones? Have you got your imaging of abdomen for presence of any urinary stone/s? Usually in a stone performer, a low back pain may be an indication of a stone in the lower part of ureter. Also, your tiredness may be due to loss of protein from the body. Hence in my opinion, you need to go for imaging of abdomen for any presence of urinary calculus etc. as well as a complete examination of the urine, particularly for presence of proteins as a first measure. Further treatment is to be done under guidance of your doctor, if needed. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Satnarain Bansal, General & Family Physician