Why is my right breast squeaking or rubbing ( like 2 balloons rubbing) after 18 weeks? (photos)

You are still very early in the post-operative period. It typically takes 3 - 6 months for the swelling to subside and and implants to settle into proper position. Swelling usually accounts for 10 - 15% of the initial post-operative appearance. The implants may swell asymmetrically, as in your case, but usually settle evenly. Please discuss your concerns with your board certified plastic surgeon. Also, make sure you follow all of your plastic surgeons post-operative instructions regarding level of physical activity and use of a support bra. Hope this helps and good luck with your recoveryRegards 

This type of noise is not uncommon shortly after surgery from fluid. It almost always goes away.The time frame from your operation makes me believe that you have capsular contracture. I have seen this before. This would be the most likely cause or problem.Please see your doctor for evaluation. Everything will be ok. Don't worry.Best wishes!Dr Chris Saunders 

It may be a rubbing sensation against the rib cage or against scar tissue?  Difficult to say without a proper exam.