If you have any questions or concerns about your body that is outside of what you read about is "normal" it's never a bad idea to go to a doctor and have it checked... Around age 18, or whenver you become sexually active you should also go have regular checkups with a Gynocologist. (you've got one body, it's up to you to take care of it
I honestly dont think there's any such thing as a normal cycle anymore, age, stress, diet, exercise pretty much anything can cause your cycle to veer off kilter. Especially if you are younger, your cycle can be a little erratic.