I end up getting into a loop when I try to purchase Minecraft from my PC

I can not purchase Minecraft from the Mojang website. I keep getting put into an endless loop of logging in, try to purchase, then asks me to log in again, then I try to purchase, then I have to log in again, then I try to purchase. etc. etc. etc. I am getting very frustrated. Please help!!!!
I don't know if the version is correct as I seem to be unable to purchase it!