Well depending on how long you have been with this particular boyfriend it may be a problem! There is defiantly nothing wrong with spending some quality time with your mother but obsessive quality time can be a issue. Are you with her more then him? Does she know everything about the relationship ? Does her advice affect the way you handle relationship situations? If you answered yes to even one of those questions, You should evaluate weather you want to really have a life with this man!!
When you are in a serious "healthy" relationship your boyfriend/Fiancé/ Husband becomes your new family. The purpose of dating is to find a person that YOU can create a home with.Your mom should understand !
-- Hope This helps
xoxo Signed with a Kiss