Is there an official page to check if PSN is down?

Yes, Sony has an official PlayStation Network service status page on the PlayStation site that shows each service, account management, gaming, store and so on, as up or down. That's the one to check first. If it says everything is fine and you're still having trouble, it's your end or a regional thing. The downdetector style sites are useful too because they show user reports before Sony admits anything, but the official page is the one that confirms it.