It hurt me all night and it was so hard to bear it sothat I went to the hospital early in the morning. It hurt all night and was so hard to bear that I went to the hospital early in the morning.

The dentist said that my toothache was terrible, and it needed a long time to treat, and I should go to the hospital three or four times over half a year. The dentist said that my toothache was terrible, it needed a long time to treat, and I should go to the hospital three or four times over half a year.

While "hospital" is technically fine, I assume you meant "dentist". Usually I say "the dentist" to refer both to the dentist himself as well as the physical location. Also "dentist's office"

She also told me to take medicine three times a day and not to eat spicy foods. She also told me to take medicine three times a day and not to eat spicy foods.

I think "not to" is fine but I'd say "to not".

It's really a bad news to me, because I love spicy foods so much. It's really bad news to me, because I love spicy foods so much.