You can be married and not live together for various reasons. Must be married 3 years
Must have resided with the USC spouse for those 3 years.
Spouse must have been USC for all the three years
Occasionally, one of the married couple has to live away from the marital home for a reason.. study, work, internship…to name a few.. And they will struggle to provide evidence of living in marital union .. but you haven’t even been married for 3 years, so this unusual situation does not apply to you