There are several synonyms for the phrase "my goodness." Some options to express surprise or amazement include "oh my gosh," "oh my word," "oh goodness," or "oh my heavens." If you want to convey shock or disbelief, you could use phrases like "good heavens," "good grief," or "for heaven's sake." Other phrases that communicate a sense of wonder or surprise include "gosh darn it," "holy cow," "gee whiz," "blimey," or "crikey." These phrases can add variation and interest to your language, while still expressing a similar sentiment to "my goodness".