One of my Breasts is Loose and Sliding Around in the Pocket- What Can I Do?

I would like to see photos to really try to see what is going on but probably you need to go and talk to your surgeon and see what type of revisionary surgery he/she recommends for you to achieve better implant placement. It sounds like capsulorrhaphy is what you would need.

Breast implants, whether above or under the muscle, are held in place long-term by the scar capsule that forms. If it is out of position after 4 months, then it will likely need to be revised. Most of the time this can be accomplished with a procedure called a capsulorrhaphy. Of course without personally seeing you it is not possible to make a definitive recommendation, but it sounds like something that can be fixed without a significant recovery time.