In this context, 'it's a little too much' means you are being too direct; you are straying out of social norms; you might be considered impolite. When something is 'a little too much' the context fills in what it is too much of.
"You're too much" after telling a joke means you are funny.
"That dress is a little much" when dressed up for a casual situation means that you didn't need to dress up that much
However, this phrase is usually used lightheartedly, even jokingly sometimes.