relatedTo currentUser AND entry
If you take a look at the Relations page from the docs. The last example at the bottom of the page shows how you can do a query using AND for multiple criteria.

The example from the page:


  Passing Multiple Relation Criteria
  
  There might be times when you need to factor multiple types of
  relations into the mix. For example, outputting all of the current
  user’s favorite cocktails that include Gin:

{% set gin = craft.entries.section('ingredients').slug('gin').first() %}

{% set cocktails = craft.entries.section('cocktails').relatedTo('and',
    { sourceElement: currentUser, field: 'favoriteCocktails' },
    { targetElement: gin, field: 'ingredients' }
) %}

  
  That first argument ('and') specified that all of the relation
  criteria must be matched. You can pass 'or' instead if you want any of
  the relation criteria to match.


Hopefully that'll point you in the right direction.