what is the difference between?
1) i really am happy & Could be in answer to a question by a mother/friend who asks "Are you happy with him/her?" The mother/friend might have had doubt about the feelings of the other person.
i am really happy This could be an answer to a similar question, such as "How are you feeling?"
2)i sure am & this is just more emphatic than the plain "I am"
I am not a teacher, but remember, that "I" in english is always capitalized.