This means that your database is corrupt. You can run DBCC CHECKDB to get an idea of how bad the situation is. DBCC will also tell you which repair option that is needed to get rid of the corruption. In many cases, it will say that REPAIR_ALLOW_DATA_LOSS is needed.
If that is so, you should first take a full backup of the database in its current state. You may or may not need it later. Next, you should instead restore a clean backup. Note that if you restore a backup from yesterday, you should run DBCC on this backup as well, as the corruption may have been lingering for a while. You may have to back a couple of days and restore full backups + log backups to get a corruption free database.
Note that this sort of corruption does not happen out of the blue, but it is almost always the case of malfunctioning hardware, most often the I/O subsystem. Unless there have been recent incident like a power failure, you should consider hardware tainted and try to move to a new platform as soon as possible.
I should add the discussion above assumes that you have a critical production database. If this is only personal development database, you may be less strict in the recovery procedure.