Breast implants far apart & pulling sensation on left breast increasing after recent mammogram (Photos)

Thanks for your question. It doesn't look like you're bottoming out but you may have some "lateral displacement". This is when the pocket stretches laterally. When you lay down the implants migrate to the sides. It should be noted that natural breast do fall to the side as well. So a small amount of this is quite normal, especially with submuscular placement. When it's excessive it can be more bothersome.
If it's bothering you enough a revision surgery is necessary to correct this. The pocket can be tightened internally to make the implant sit more centrally. Since your implants are 8 years old I would recommend switching them out for new ones. Risk of capsular contraction or more scar tissue is relatively low for revisions surgeries but proper no touch technique protocols should be followed.
The mammogram isn't likely to blame for this. It may have inflamed or bothered a muscle but I would suspect that'll improve in a few weeks.

You are not only unhappy with the aesthetic appearance of your breasts separating when you lay supine, you also have symptoms from that separation. You've been told by your surgeon that the risk of capsular contracture from a revision surgery would be too great, yet he performed your surgery through a periareolar incision, which put you at highest risk for capsular contracture when compared to either transaxillary or inframammary incisions. First he/she didn't care about increased risks, now he/she does? Hmm. I would get a few more consultations. The surgery you need is called a capsulorrhaphy and is essentially bloodless, owing to only scar capsule needs to be tightened, and no new tissue cutting is necessary. The real question is do you do it through existing scars (which are fairly prominent), or go through new inframammary incisions, as per evidence based best practices. Something to discuss while on consultations.

Your breasts are low on the chest wall and are displacing inferiorly and laterally. Your alternatives are smaller implants or removal of implants or reinforce the pocket with either sutures or mesh. The technique I recommend is explantation with lift using The Bellesoma Method. The implants are removed, your breast tissue is reshaped creating upper pole fullness, elevated higher on the chest wall and more medial to increase your cleavage. Vertical scars are avoided, nipple sensation (in 95%) and the ability to breast feed are maintained if not injured during your previous surgery. Later, fat transfers or small implants can be placed if additional volume is desired.

Best Wishes,

Gary Horndeski, M.D.

although your second photo is not clear if you are standing, it appears you may be bottoming out some. Naturally, you have space between your breasts and the bases of your breasts cannot be moved, Fat could be added to your inner breasts for a little more fullness.