hi and welcome to beyond blue.
just to make sure I am on the right page, are you saying that being sad makes you feel happy/smiling?
perhaps you could give me an example of when this is happening? and tell me your thoughts and feelings?
as for whether it is normal - it is for you. It's a question/statement I will tell my psychs and the reply I get is "what is normal?".
I am listening to you so please tell me more.