It sounds to me as though you are doing the right thing—continuing to let him know that you love him. But let me add that it is important you not do anything to suggest that his new interest in his father is in any way a bad thing. What you are describing is a new attachment—a deep emotional relationship with another person. Babies generally develop their first attachment around 7-9 months of age, almost always to their mothers. But around your son’s age, they begin to develop additional attachments; fathers are usually the lucky ones to be the main character in the establishment of this second major attachment.
It’s actually a good thing. For one thing, you want your child to have a close emotional bond with someone in addition to the one he has with you. For another, attachment is a two-way street. As your baby becomes attached to his father, his father will become more attached to him. And what could be better for a child than to have two parents who are “hooked” on him. Don’t worry about his current coldness to you. I think this will fade in a short time as your son realizes he has two parents who are devoted to him and that he can actually love more than one at a time!
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.