I have asked this question to my doctor. (I have county health insurance and it seems that these doctors either do not know the answer, do not care to give the answer or do not want to take the time to tell me what is possibly happening inside of my body).
I posted this question on yahoo! Answers as well. No clear answers yet. I want a very detailed descriptions of what could be happening inside my body. I am not pregnant.

I have no children.
If you are a nurse or if you are a student nurse and have taken micro-biology, can you please help me out here.

I need details.
I'm 33. For the past 4 years, I have had to go pee like crazy (about once every hour) while on my period. I do not have this problem when I am not on my period. I do not have to drink water to pee like this during this time of the month. I have been told that I "retain water". Okay. What does this mean?

Paint me a picture.
Why do I pee so much only during my period? It is crazy

having to go to the bathroom every hour. If I was working, my boss would wonder why I'm not getting any work done one week out of the entire month. My boss would wonder why I'm always in the bathroom. I do not need to drink anything. When I am on my period, I just pee. All the time. The day that I'm done with my cycle-it's all over. My body is back to normal!
So, what is going on? Are all of these little cells in my body just dormant for three weeks out of a month and all of a sudden-bam! These cells just fill up with water and go to my bladder and then dump water there and then I need to go pee? Or do these cells go to the uterus? I need a very detailed description of what is happening.
Can my weight be a factor in this? What about my age? I am 5 foot 1 and 180pounds. When I was in my 20's, it was not like this! Is this a common event that happens in women in their 30's? Is this a common event that happens in all women when they are on their period? I am not a diabetic.
Is there anything that I can take to stop this urination? Is there something that I can take besides the pill? I'm sure that the pill will help since that is meant to stop the cycles (such as 4 cycles a year instead of 12). What about Deterol LA? Would this help if I took it only during my period?
Please help me! Thank you
Sandra