Passing blood clots in urine, burning with urination along with severe pain are symptoms of passing kidney stones.
When the blood in the urine is at the beginning of urination, it most likely comes from the urethra, (the tube from the bladder to the outside), when throughout urination, the bleeding source is bladder or kidneys or ureters (the tubes connecting the kidneys and the bladder), and bleeding at the end of the steam indicates bleeding from the bladder.
Burning with urination could be from the kidney stone irritation or due to urinary tract infection that are common with kidney stones presence (kidney stones are contributing factors for uti).
You may ask you doctor for alpha blockers, drugs that help body to pass the stones more quickly.
The average time a stone takes to pass ranges between 1 and 3 weeks.

thank you very much, but the blood comes after urination. =/