Question about a little boy being weird with his dog.

I know that this question may sound a little weird, and it may get some crazy responses, so please only give feedback if you are serious.

I have a 5 year old son who is making me a little worried. Over the past few months my wife and I have noticed him playing with his penis while in the tub, or on the toilet.

For a while we were thinking that this just may be a part of him getting older and discovering himself (or whatever). But today we caught him hiding behind the playground in the back yard with our dog, and when I called for him to come inside, he hesitated and finally came out with his pants unbuttoned. When I asked him what he was doing he told me that he sometimes puts his "peepee" on the dog. And of course I was shocked and continued to ask him questions about why he does that and he also told me that he allows the dog to lick it!

I was so embarrassed and did not know what to say or do. He does not act like it bothers him, nor does he try to hide it from us. I just don't know what to think...

So my question is: has anyone ever experienced anything like this with their children and if so do you have any advice for us?

BTW, His mother and I are still together and we have made a good home for our children. This is not something he has witnessed in our home (before you get any ideas!) Just looking for some direction.

Dad