Dear Energetic448638,
breast implant type and sizing selection is a complicated process and requires a detailed consultation that includes a discussion of your goals, a detailed examination, and a lengthy discussion. But the decision will always start and end with the patient. When it comes to...
If you are bothered by the asymmetry, then it can be improved with differently-sized implants and/or fat transfer. While no one's breasts are perfectly symmetric, they can be made closer than what you have now!
Your breast are likely getting larger with pregnancy. This is certainly stretching the nerves supplying the nipples. Once you have expanded to you maximum size, the pain should subside. There is likely nothing stopping you from breast feeding as the apparatus of the breast tissue, ducts, etc is...