fussy baby

My son just turned 3 weeks today and he's a very fussy baby. The doctor says that it's too soon to be colic. He was 8lbs 10oz when he was born so he was a big boy and always wants to eat. I feed him constantly and that seems to be the only thing to calm him... yet sometimes he just sort or uses me as a pacifier! Does anyone have any advice on what to do or what may be the problem? Also, will he grow out of this? If so, when?