That same thing happened to me too (I replied to another question)
Before I met my current boyfriend, I lived with my mom. She kinda took on the role of the second parent, because obviously at times, I needed help.
My son used to be so attached to her. He would scream and cry when she would leave the house. And he always wanted grandma.
Its really just one of those things that you have to give time. Eventually, he will see that you are the one there all the time now. It fixed itself with my son, I see no reason why it won't with you.
at 3:01 AM on Jan. 17, 2009