Yes! Don't stand under it! Actually, your problem is not terribly uncommon. There is a good possibility that your home was built before chimney braces at the roof line were required, and the earth below is settling (Leaning Tower of Pisa Syndrome). If your fireplace has a poured in place concrete footing, there is the remote possibility that the whole thing could be brought back into plumb. But doing so is iffy and not very cost effective.

For now you must insure that your home is protected against unwanted water traveling into the exposed area. A sheetmetal contractor may be able to help you there. Flashing connected between the house and the fireplace is a must. Next, a repair contractor should be called who can install connectors between the house and the fireplace to help prevent future separation. Also, it would probably be a good idea to ensure that water is prevented from puddling around the base of the fireplace in order to hopefully slow the ground settlement process.

A possible economic solution: If you are retired and on a fixed income, you should check with your city administration department or the county to see if grants are available to help make your repair. Don't get your hopes too high, this kind of funding has been rare lately- a waiting list might be the best you can hope for.