Okay, first off - take a deep breath and move slowly. You can figure this out without destroying everything if you remain calm.
Verify you're still being asked for the same information on login. concrete5 has two ways of logging in, either using your username (ie: "admin") or your email. Sometimes an upgrade or something might cause your site to go from using one mode to the other. If you're used to logging in with a user name and all of a sudden it's asking for email, that can be very hard to realize, and it will make it feel like you simply can't login without resetting your password. Take a second to read what that login page is asking you for, email or username?
Try resetting your password. At the bottom of that login page is a forgot password form. Put the email address you used to setup Concrete5 with in there, and it will send a email to that address with a link to reset the admin's password. EVERY Concrete5 install has a root admin account, and EVERY install has to have a email associated with it.
If you don't get the email to admin, several things could be going on. Perhaps the email address just isn't something you actually get emails at. Perhaps something about the server is keeping mail messages from going out. Regardless, you're going to need database access to proceed further. Using PhpMyAdmin or some tool to get at your database, find the Concrete5 database and look for the LOGS table.
In the LOGS table you will see at least one row. This is a copy of the email the system just tried to send to your admin account. Even if you brilliantly setup concrete5 with a fake email, the message Concrete5 is trying to send will be logged here. Go ahead and look at the content of that email. There will be a link in it. Click that link.
You will now be taken to a reset your password interface. Use it. You're in.