contact of the editor
Contact the editor. It happened to me once that the referees were divided, so the editor sent the paper to more referees, hence prolonging the process. He just forgot to notify me. Moving to another journal is a bad decision, since you haven't been rejected yet. What if then you are liaising with two journals and both accept it? Not good.

Also, check the average processing time of the journal. Some do take long time, even up to six months!