It doesn't appear from your photo that you will have enough fat to harvest to make a meaningful change to the size of your breasts.
Your photo does suggest that you don't have much in the way of donor fat sources for augmentation purposes, but if you do have some fat elsewhere, that is certainly an option.
I agree that most of your breast volume does seem to be along the lower pole of your breast tissue, but a breast enlargement is never truly necessary. If you would like more volume, then an augmentation makes sense. An augmentation would also be an ideal opportunity to try and address some of the volume discrepancies between the two breasts.
Meet with a boarded plastic surgeon to discuss your options. Best of luck!
Options for Breast Enhancement
Fat grafting has the advantage of using your own body's material to increase breast size, but only small augmentation is possible and it is just gaining popularity and long term results are not yet available. There is always uncertainty about how much fat will "take", increasing the possibility of asymmetry and need for revision. Many plastic surgeons are still concerned about how the fat that did not take looks on mammograms, and if it will increase long term false positive results. Be sure to consult with a board certified plastic surgeon to help you navigate this decision. Good luck!
From the photograph, it's my impression that your breasts have taken on the look of a bottomed out breast implant. There is more breast gland below the nipple then there is above. A simple fix to not only increase the amount of upper whole fullness but also create a more acute angle at the infra-mammary crease, would be to take out a long transverse wedge of skin such that when closed, the distance from the nipple to the crease has been shortened forcing the breast tissue upward. Fat grafting with prior use of a Brava device which stretches the skin and fat, allowing more space for fat to be placed has been described and has been shown to be better for fat retention than fat grafting alone. In somebody thin as yourself, it's been my experience that a lot of areas ,as far surface, need to be taken in order to have enough fat that it would matter. Good luck.
Fat Transfer Breast Augmentation
Thank you for your question. Fat transfer can augment the breast is a very natural way. Based on your photos and concerns, you are unlikely to have enough fat to get signficant augmentation. Further, you expressed concerns about a flat upper pole of the breast. Fat is not very effective in filling out the upper poles. The breasts would be larger, but the upper poles would still be flat with fat transfer as they are naturally. A breast implant is still the most effective way to fill the upper pole of the breasts effectively and permanently. Best wishes!
More pictures from lower body
You have good amount of breast tissue ,but your breast is bottoming out due to low inframammary folds. I would like to see your lower body pictures and would suggest to fix the inframammary fold position.
To be a candidate for fat grafting, you must have some available fat to use. Your one photo does not show much usable fat. I would suggest meeting with a board certified plastic surgeon and discussing the options of fat grafting and using implants placed behind the muscle for more upper fullness.