I have a period every month but i bleed for 9 to 10 days and my period stops after 4 days and then starts up a couple of days later why?

Start and stop: Your period sequencing is obviously abnormal and causes me to 'start' thinking of solutions for you. Most of the causes are ones that require a gyn md to evaluate, so 'stop' wondering and make appointment with one soon.

Common, depends: It is common for menses for such periods, but more than 8 days is considered abnormal. It is not shocking to stop and restart, especially if it is a recurrent issue for you. If you are older than 35 it is prudent to obtain a biopsy or sample of your uterine lining to assess for cancer, though this is less likely. Finally, an pelvic ultrasound can show polyps or fibroids causing the bleeding.