Revision for one breast being smaller than the other after reduction? (Photo)

I am 6 weeks post op and I have one of my breast that are smaller than the other. I have let my PS know of this and they advised me to wait until 3 months then we can talk about revisions. I prefer the bigger breast than the smaller one. What you advise to be done in this case? Implants? Fat transfer? I do not want lipo from the bigger side as I like that size much more than the smaller one. What causes the breast to be asymmetrical?