Breast augmentation 5 days ago and they look smaller than I expected. Will the size increase?

When implants are first inserted, they sit high up because your tissues are tight and gravity hasn't taken effect. Over time, natural tissue expansion occurs to allow the implants to fall into place. By this time, your breasts will have taken on a more natural contour, where the lower breasts become softer and rounder. Please wait at least four months for this to happen.This process tends to occur sooner in one breast than the other, so don't be alarmed if you find that your left drops before the right or vice versa.

It is too early for you to see much of a final result.  However, initially, breasts tend to be swollen and larger than their final size.The difference between C and E is significant, it is unlikely that Cs will grow into Es

I'm sorry to hear about the concerns you have after breast augmentation surgery. You should be aware that it is not unusual for patients to feel that they are “too small” or “too big”,   early on after breast augmentation surgery.  Most patients who feel this way ultimately are pleased with the results of surgery in the longer term. Many patients who feel that they are too small immediately after surgery find, as the breast implants “drop and fluff”,  that the breasts actually appear larger to them.
 I routinely ask my patients  to wait at least 3-6 months before   evaluating the end results of the breast augmentation surgery.  This waiting time allows patients to (uaually) physically and psychologically adapt to the new body image.  
Obviously, it is best for patients not to be making important decisions ( for example about the results of surgery and/or the need for additional surgery) while they are experiencing the common post operative emotional “ups and downs”. In the longer term, if you still remained displeased with the breast size, communicate your concerns with your plastic surgeon in a calm and constructive fashion. Together, you will be able to determine whether increasing breast size can be safely done. Remember not to communicate your goals in terms of achieving a specific cup size, which can be a source of miscommunication. Best wishes.