What Causes Irregular Periods While On Implanon?

Hi, I have had the implanon for about 2 years, occasionally get sharp pain where it is located. Very irregular periods. Should I be concerned about the pain? As far as I know, it is not bent. I am 21 years old, average height and thin for my body shape. I am sexually active, and have been under immense stress in the last 5 months.