I have a 61 year old rambler. It's developing cracks in the walls. But the biggest concern is the bowing in the ceiling, exposed nail heads. I'm not sure what to do next? Thanks

You need to have a structural person look at the problem. I would guess some type of foundation issue. Do you have a large load in the attic?

Can you access your attic

Cracks in the wall and bowing in the ceiling sounds like foundation problems. Sadly that's not something most people can deal with by themselves. Time to call the professionals.