Xbox 360 got hacked after playing Modern Warfare 3 match?

Hi all,

Unfortunately, my Xbox Live account was hacked, and I am no longer able to connect to Xbox Live or access my Account Security settings. The second part is the most alarming to me.

A little bit of backstory, I was playing Team Deathmatch in MW3 and kept getting spawn killed/wall-shotted/insta-killed by a hacker who I ended up getting in a heated text conversation with. He ended up logging me out of my account, finding what city I live in, slowing my Wifi, and disconnecting me from Xbox Live completely.

Along with this, I am unable to access my Account Security option through settings, my Wifi is slower now, AND the associated email with the account is my main email! How worried should I be? I will call Microsoft Support Line in the morning, but does anyone have any other advice or ideas?

Thank you very much in advance!!!