you should go to the doctor because i don't think that is normal
You probably should see a gyn just to get some peace of mind. I have a 21 day cycle instead of 28 days so I often have a period twice in one month although not every month. Sometimes really bad sharp pains low down in your pelvis during your period are a result of passing blood clots. Not saying this is the case with you but I have had it happen.
You do need to see an ob-gyn. It could be that you have polycystic ovarian syndrome, which is quite common. Often it's identified by infrequent or lack of periods, but for some of us- me for example, the periods can be unusually frequent, heavy, and long. There are many reasons that you could be having multiple periods and the best thing you can do is have yourself checked out. Good luck!