Breast implants too small but told I can't go bigger?

I had breast augmentation 5 months ago and had 325cc (textured silicon implants) put in but now I think they are too small. I cant get a cleavage or the look I want without wearing a push up bra. I initially told the surgeon I wanted a full c cup (so he suggested 300cc or 325 cc)but I now realise that a full c is not very big and wish I had chosen 350cc!

I can also really feel (but not see) my implant underneath and around the sides. My surgeon said I can not go bigger as you would start to see the implant, but all of my friends have bigger implants and they look good and they are all slim like me. I am very dissapointed and upset that I have to wear push up bras and that I cant go bigger. Is this true about not being able to go bigger? and will I be able to eventually see rippling from my current implants in the future if I can really feel them now??