After having a modest increase in size with a breast aug. in May, can I now replace the implants with larger ones?

I had silicone implants placed under the muscle in May. I thought I wanted a modest increase but now feel like I should have gone larger. This is not my doctor's fault as he did what I asked and I thought the 250cc implants would be enough. Is it too soon to go back and ask for larger implants - I am looking for increasing my breasts another inch. I was an A cup, now I'm a B cup, and I would prefer to be a C cup. Instead of changing the implants, should I get fat transferred to the existing breasts to supplement them? Thank you for your time.