The pain you are experiencing is due to muscular contraction attempting to propel your stone down from the kidney towards the bladder; unfortunately, you have no control over these contractions.
If the stone is too large to pass by itself or if the surface of the stone is "spiky", this causes the stone to get stuck and the muscle contraction becomes more powerful. It is this which causes the severe pain.
Powerful pain-killers may be needed to relieve the pain and, in addition, you may be prescribed muscle-relaxant drugs which can encourage stone passage.
Sometimes, an infection occurs in the urine behind the stone and this, too, can make you feel unwell with a high temperature. Stones at the lower end of the ureter (close to the bladder) can often irritate the bladder and cause symptoms very similar to cystitis (a constant desire to pass urine, pain on urination, blood in the urine & passing small amounts of urine only).
