Please Help, My Girlfriend Wants To Kill Me With S*x

Please help post on kobojamz!
My name is Kelvin (not real-name). I had actually giving up on the dating game after my heart was broken into pieces several times.
My first girlfriend was sleeping with my best friend and when people told me, I choose to give her a benefit of the doubt because of love until I caught them together in the act.
I was starting to develop trust issues with women till I met my second school mate from Crossriver Calabar, Eno (not real-name).
We immediately got along. She told me she wasn’t dating but wasn’t searching for a boyfriend too.
I tried to convince her that we are better off dating since we were secondary school mates and she was my crush back then.
She rebuffed my advances, saying that if we date, I will get tired of her.
This is a girl that is tall, slim, busty, curvy and soo beautiful. How can I get tired of such a woman?
After much persuasion, she finally agreed to date me.
Fast forward to today, I’m regretting the decision.
We have s*x for like four-times a day. It got so bad that we barely talk about anything but s*x when she comes to visit.
I thought it would reduce when I go to visit her, but it is even worse.
One strange thing I observed is, whenever she is on her monthly menstruation period, she always cuts off from me and barely reply my messages.
I try to man-up the relationship, advising her that we can do other things for pleasure than s*x but she immediately becomes moody when I refuse we havw s*x.
My people are complaining that I’m becoming slim and I observed recently that my bladder can’t even hold urine for long.
How can I teach her to stop having s*x everytime?