If you don’t want to enter your user/password every time, you can store it permanently in an authinfo file. In Emacs, the auth-source package takes care of that, but the syntax for https authentication is a bit peculiar. You have to use a line like the following
machine www.google.com:443 port https login username password secret
Note that you have to specify the port number in the URL and also specify ’https’ for the port. This is not a bug. For more information, see (info "auth"), especially section "Help for users".
Since you are storing your password in a file you should encrypt it using GnuPG. Emacs will prompt you for a decryption key when it tries to read the file.