General well-being:
* I feel good. (most common and neutral)
* I'm feeling well. (slightly more formal)
* I'm feeling fine. (less formal)
Feeling happy:
* I feel great. (stronger than "good")
* I'm feeling happy. (more specific)
Feeling healthy:
* I feel healthy. (focuses on physical well-being)
* I'm feeling good physically. (more specific)
Other options:
* I'm doing well. (more about overall circumstances)
* I'm feeling alright. (less positive than "good")
The best translation depends on the situation and the intended meaning.