My left breast vibrates every 20 seconds on the dot. What could it be?

I had a breast augmentation (under muscle, smooth round silicone moderate plus 350 cc) on 5/28/15. about 2 days post op I started having a strange vibration under my left breast. It feels like a cel phone is vibrating in there. It lasts for about 1.5 seconds and happens every 20 seconds. It has continued for 2 days. It is really bothering me. What could it be?