How come my left breast has gotten bigger after my uplift and implants? (Photos)

It is probably from weight gain. You have two different breasts, and they may not enlarge equally with weight gain. At 10 months, you are settled. The difference is mild and probably will not be noticed in clothing.

It would be helpful to know if your implant size is equal on both sides.
Perhaps you had more breast tissue on the right side?
If that’s the case, then weight again could make the bigger breast gain increased volume faster than the smaller size.
Follow up with your plastic surgeon to get an assessment and talk about potential treatment options.
It’s hard to give you a quality assessment with limited information.
Best,
Mats Hagstrom MD