Parents often wonder "Is this normal or should I be worried?" I think that starts pretty much from the time you know you are pregnant! It seems like just when we have our kids figured out, they change. And that's true. Some developmental phases can last only a few months. But, sometimes you get a feeling that there is something wrong.
If your child has changed in a way that concerns you, listen to your intuition. You know your child! Don't be embarrassed to ask for help or for an objective opinion. It often only takes a session or two to figure out a new technique to help your child, or you, through a "phase", or to head off a deeper problem.
Here is an article that can help parents know when to seek help: "Facts for Families" from the AACAP