Mutisite subdirectory help

This is driving me nuts!!! I have installed wordpress, followed all the instructions on how to add multisite, but here’s the rub. I want to keep my main site (let’s say mysite.com) completely blog-free. One blog will be at mysite.com/blog and another to be at mysite.com/anotherblog. However, when I upload wordpress to mysite.com/blog it forces me to use subdomains like mysite.com/blog/anotherblog

I’m so lost!! If anybody can shed some light on this I would be forever grateful!!