It appears your user accounts are misconfigured. This is how it looks on my system:
Notice how the user is in the sudo group, this is necessary to use sudo. To add your user to a group use gpasswd. In your case it should be:
[ isamu: ~ ]$ groups isamu
isamu : isamu adm cdrom sudo dip plugdev lpadmin sambashare
The above command needs to be run as root. Root is the actual admin account, the user that can do anything, it's present on every system. To log in as root use:
gpasswd -a me2 sudo
and enter your admin password.
It seems strange that your user is only in it's own group. When creating new user Ubuntu automatically assigns user to groups to allow some basic tasks. See my groups output at the top, I'm in several groups and I didn't add any of them manually, this is the default.