No, not only you. On Tuesday night Pacific Time, YouTube was down for many users. The failure seems to have started at 18:15, which means a rather long downtime for such a big website.
The company is aware of the problem and twits its updates. The account responded to tweets reporting about the failure about an hour ago and has since painstakingly responded to many, many reports from users.
Youtube is not often downtime, which makes Tuesday's downfall quite remarkable. We've notified YouTube of the cause of the failure and will update this story as we learn more.
Update 20:00 Pacific: Google confirms that YouTube is back online and should work again for all users.