Could be either to be honest.

Can you not access your website at all? Or can you only not login via the backend?

Who is your host? Ask them if there is downtime..

Most likely just a problem with your host.. either server issues or someone on the shared hosting has utilized all the cpu and caused a temporary server meltdown.
Hackers usually do much worse things that disconnecting your database.

Contact your host. It's a technical problem. Also try checking using proxy.

Claim down.
It may be the hosting company's problem.
Just contact them during their working time.

Next time, you should choose a company that has better support.

Keep update let us know.

You need to contact them, usually the most common cause is the connections being maxed out.

if this happened to me I would say major problem, but I don't know your setup, I use vps.

try to go over the changes you made recently and reverse them then see if it connects to your database.

it could be anything. could be a hack or a problem with your program. bottom line it's broke.

i was reading this and can imagine you getting stressed, i know i would thinking my site was hacked.... But thats good its workign again, i think this was my adrenaline rush for the day haha, its always best now to keep relevant contact info for your hosting company in case this occurs again and you need to contact them, out of interest what was the issue?