Why does my implant feel like it's popping out of place?

Thank you for your questions and I am sorry that you are having continued issues with your implants.  It sounds as if you may be having a capsular contracture issue, where your body's scar tissue is squeezing down on your breast implant, and chest, causing your dull pain, and popping sensations.  I would recommend you follow up with your surgeon and voice your concerns.  With an in-person assessment the cause of your symptoms can be diagnosed, and a treatment plan to correct the issue discussed.  Hope that this helps.  

I would encourage you to schedule a visit with a Board Certified
Plastic Surgeon immediately to determine the exact source of your
discomfort.  You will certainly require a
clinical examination and may also require additional imaging studies such as an
ultrasound, mammogram, and/or MRI.  If
these indicate a rupture, your surgeon will likely encourage you to proceed
with surgery.