Do people who are happy, positive and nice ALL the time give you the creeps? Or is it just a me thing?

I'm certain many people probably think of me like that. I try not to have negative thoughts and when I do, I usually keep them to myself. 
I also tell the truth when asked a direct question, or when my opinion is asked for. I try to be empathetic and kind, but even so, it's not always well-received.