should I buy size 3

My daughter is only 2 months old she's about 14 lbs doctor says her weight is fine but she looks like a 6 month old to me.. And barely fits size 2 diapers should I go and buy the next size I'm not sure??

About Kari
Born: Sacramento, California
Current: West Sacramento, California
Birth: August 10
On since: May 5, 2014