We had a 4/12 roof pitch and wanted more of a slop. We hired a guy who built a 6/12 over the top of the first one. Now we are having trouble with our ceilings. Is there too much of a load with two roofs on one house? We are having drywall cracking and ceiling is starting to sag. What do you suggest we do?

That never should have been done without an engineering study. The only way it can be done without overloading the roof would have been to use trusses. What you are seeing is to be expected, you have added what is equal to 2-3 roof covers. Might be able to add some interior supports but not sure how that would look.

I doubt it was even legal.
I agree that now you need a structural engineer. You may have to start from scratch. Or at least rip off the top roof and redo the shingles.