What's the problem with my bike?

If you’ve got a Walmart bike, then the problem is….it’s a Walmart bike, and you need to just break down and spend some dough on a better one. If you’re riding a Raleigh touring bike, then something has become misaligned/needs recalibrated or something that a bike shop would have to fix. Those gears and deraileurs are semi-precise devices and are tough to work on unless you know what you’re doing. Had the same problem, until I got my Raleigh ;)

Edit- and I say ditch the cheaper bikes just because there’s not much you can do for them, low quality is low quality. If you install a better deraileur it’s not going to do any good if the gears are slightly bent or the bike frame isn’t straight.

Could be your rear wheel has moved in the dropouts, your rear derailleur could have suffered a bump (perhaps while locked up somewheres) or your chain simply needs to be replaced.

I would take it to a local bike shop to have it looked into.

For some reason, the chain is too lose. It could be what @gemiwing said. It could be that something about the derailleur has changed. It could be, as @iam2smart99037 said, it’s a cheap bike and maybe the chain is too long and you need to take out a link or two.

Make sure the derailleur is not bent and stll alligned with the chain and teeth

In what way? It should ride on the guide and tension pulleys in the center of the cage unless the derailleur got bent so far sideways that it can’t. Unless you mean the front derailleur. That’s just an adjustment, there should be a couple of screws on the top of the derailleur you can turn to stop it rubbing.