What Causes Vibrating Sensation In The Abdomen With Irregular Periods?

I am currently on the pill and PMSing. I've felt bloated the past week, but for the last few days I have felt this weird vibration in my lower abdomen below my belly button and in my upper pelvic region. I have had a light period for several years now because I had an eating disorder 4-5 years ago, and my period has slowly been getting back to normal. I have been on Lutera since that time. I am not sure what is wrong with me or if this vibrating is even related to my period.