Now that you have your username, you can find your ID! Just go to http://graph.facebook.com/USERNAME and you should see something like the picture. You can check mine at http://graph.facebook.com/jordan4762
Ok, a few years ago you could find the URL to your profile picture to get your facebook ID. But facebook changed that, and people who changed their username (http://www.facebook.com/USERNAME) can't find their ID. So I have this little trick. Its really easy. Enjoy =)
Ok, go to your account settings (https://www.facebook.com/settings?ref=mb ) and look at the username box. If you can now find your username (look in picture) it should be in the middle of the page. If it is not set, press the edit button and set it.