What do I do if I discover problems with the house that were not there or I didn’t notice when I put in my purchase offer?

Contact your attorney. If the problems are sufficiently significant and you notice them during your walk-through inspection, they can be addressed and hopefully resolved prior to closing. If you notice them after closing and they were misrepresented to you by the seller or the real estate agents prior to closing, you may be in a position to seek legal remedies from the seller. Otherwise, you may be out of luck.