Mamas boy!!! what to do!!!?

My bf is 22 and we've been together for a while now i love him very much BUT!!! he hasn't cut the umbilical cord!!! if his mom leaves town for a day he gets stressed out and sad because he feels his mom is too far from him...then when we visit her he says she looks sad so he gets sad!!!! he and she complains that they don't see eachother enough...!!! we're engaged but i like independent guys and i try to understand his mom is a little sick...am i wrong when i tell him that he needs to let go of his mom a little?