I get them also lower right at the top of my ass-I thought it was possible kidney issues also because I was on week 4 of a pretty heavy cycle with a few different compounds(some oral) but I spoke to various sources and all said the same thing,'BACK PUMPS',and as long as urine was not discolored and no other symptoms occoured not to worry,and sure enough it passed and it still will come back from time to time but always goes away.Weather thats what it was or not,who knows?But these were creditable dudes.