Has my silicone implant ruptured? (Photos)

If you are currently breastfeeding, than I suspect any changes you are seeing are more related to that than anything.  The breasts can change dramatically and appear completely different from each other throughout that process.  I would not worry about the implant itself.  Even if a silicone gel implant gets a tear in the shell, it generally does not change shape in any way. I hope this helps.

Thank you for sharing your question and photographs.  Unfortunately without an in-person examination it is difficult to offer definite advice but I see your area of concern.  Most likely this is a capsular contracture which has caused your implant to settle higher on your chest, leading to laxity of your lower breast.  See your surgeon for an evaluation, they can offer you the appropriate diagnosis and treatment plan.   Hope this helps.

Silicone breast implants have evolved over the past 55 years. The current generations of implants have a more cohesive (structured) gel and a more durable shell than the implants that were available prior to the 1990's. 
Implant ruptures are uncommon and when they occur, due to the construction of these 4th and 5th generation devices, the gel remains in the normal scar capsule around the implant. "Silent" ruptures can be difficult or impossible to detect on clinical exam and require either an MRI or high-resolution ultrasound to diagnose. The FDA recommends that patients obtain screening MRI's every 2 years starting at year 3 for this reason. That being said, many/ most patients do not undergo this testing since the risk of rupture is very low and the risk from the rupture is even lower.
When an implant "rides up" it is much more likely that a capsule contracture has formed. When this happens, the normally soft and thin scar tissue around the implant becomes more reactive and tightens. This makes the implant lift upwards and feel firmer. Contractures may or may not be associated with an implant rupture. 
Capsule contracture is managed with a revision surgery when the scar tissue is either removed or a new implant is placed in a new pocket. This surgery is very common and recovery is usually much easier than the original augmentation.