I think your son is paying you a compliment. He isn't favouring dad, he's secure in the knowledge that your always there and doesn't need to seek out your attention because its on tap, whereas dad (presumably) leaves to go to work so when he's home he needs his attention more.

As for strangers, be proud of yourself for raising a little boy thats secure enough to safely enjoy the novelty of there company.

I wouldn't change anything

Thank you so much for replying, you have actually made me cry (and in a good way this time, unlike quite often recently). I had never looked at it like this but will try to from now on as what you said made sense and as my husband is out all day maybe that's why he is like he is. This will help me when it looks like he doesn't even know I'm here!!! Thanks again