I have slight rippling between cleavage, will this get worse? What am I to do? (Photos)

You don't appear to have much actual breast tissue, but fat grafting, if you have donor fat, could be added. Yes, breasts naturally fall to the sides when you lay down. However, your lateral pockets could be tightened so you have less movement. Doing so will make them feel somewhat firmer.

Dear MrsBA,
I understand your concern. However, without a proper assessment, it would be difficult to determine what went wrong. It is best that you visit your plastic surgeon for further assessment or ask for a second opinion. Only after a thorough examination, you can get proper recommendations and advice.
Daniel Barrett, MDCertified, American Board of Plastic SurgeryMember, American Society of Plastic SurgeryMember, American Society of Aesthetic Plastic Surgery

Thanks for the photos. Things look pretty good and the implants look well centered on your nipple/areola complex. The reason why you feel your implants off to the side is based on the way your rib cage is shaped. However, the best indication of your implants falling out too far laterally (to the side) is your NAC. In your case, the NAC is well centered on your implants so I would say things look pretty good.
As far as the rippling goes, I don't see any, but you have implant palpability which is normal in the areas you described. There is no muscle coverage in those areas, so feeling the implant is a lot more common in those areas. As far as will things get worse, difficult to say as every persons body changes with time, so more so than others.

Hope that helps.