I think waiting 6 months before doing a revision is very reasonable. The amount of breast tissue you have was always destined to pull downwards on the breast and I suspect that you could have benefitted from a lift regardless at your initial surgery. Never hurts to get a second opinion, but i would recommend waiting. That said, you will probably benefit from pocket adjustment AND a lift. I am not sure that sub muscular implants are a good idea... they sometimes get trapped up under the muscle like yours. I use a dual plane approach in all of my augmentations so that the implant can settle properly into the pocket.
Lift breasts and keep implants under muscle
Textured implants are intended to stay where they are placed and not drop over time. I recommend keeping them under the muscle. From your photos, it appears you would be a candidate for a breast lift (mastopexy). I recommend that you wait until your soreness has resolved before proceeding with additional surgery. I believe six months is a reasonable period of time to wait after your breast implant placement before proceeding with a breast lift.
Sientra Breast Augmentation - Do I need a mastopexy?
Thank you for your question. I believe the best way to correct your problem is to perform a breast lift (mastopexy). The implants will not likely "settle" any further as they are textured. The breast needs to be lifted to a more appropriate position centered above the implant. I would not change the implant location to subglandular as this alone will not correct the problem. Hope this helps and good luck.
Wait before revision with gummy bear implants
There are two issues to consider: one is that the texturing of implants is intended to stick them in place so that they don't rotate, which means they will not settle. Second, placing them above the muscle will not correct sagging. In your case, it may be that the implants are a little bit high AND that a lift is needed. In either case I would keep them under the muscle.
Putting the implants above the muscle actually can accelerate the stretching out of the breast tissue, and make your breast droop worse over time. It also increases the risk of capsular contracture. I would recommend the breast lift (mastopexy) as the better choice.