People really need to quote the scriptures. The scripture you are referring to is John 14:11 "Believe me that I am in the Father, and the Father in me: or else believe me for the very works’ sake." But then in John 17 we have the following:
21 That they all may be one; as thou, Father, art in me, and I in thee, that they also may be one in us: that the world may believe that thou hast sent me.
22 And the glory which thou gavest me I have given them; that they may be one, even as we are one:
23 I in them, and thou in me, that they may be made perfect in one; and that the world may know that thou hast sent me, and hast loved them, as thou hast loved me.
Jesus clearly says here that he wants to be
in his disciples just like he is in the Father and the Father is in him. It is clear, therefore that Jesus being in the Father does not mean that he is the Father. It merely means that he has the same character as the Father. Just like Jesus wants His disciples to have the same character that he has so that they can have the same character God has. Matt 5:48 "Be ye therefore perfect, even as your Father who is in heaven is perfect.".