You are in the Death Realm. You need to find your way out of there back to the regular world. If you can't find your own way out then try asking another player if they will show you the way out.
Once you get out of the Death Realm you will be cursed for 30 minutes real time. During the curse your physical abilities will be cut in half. This means if you are carrying more than half the weight you can normally carry you will not be able to move unless you drop somethings to bring your weight down.
