Did you recently install any new apps, or update any apps, just prior to this happening? I ask because it sounds like something was installed and has changed your system around. If this is the case, the only thing I can suggest at this point is to do a "Hard Reset". However that will erase anything you have on the device. So I only suggest it as a last resort.
Should you choose to reset it, please do the following....
NOTE: Again, I must point out, doing this will clear the data on your tablet, so it is suggested you not choose this option unless you have to, or aren't worried about losing anything on the tablet.
To "Hard Reset" the tablet...
1. Make sure that the tablet is actually powered off.
2. Press the "Power" and the...