Hi Sarah, I am sure our pediatricians will weigh in here, but as a fellow mother I want to assure you the baby-comparing game is totally normal and can get a mom so worried! Milestones are just averages, and every baby is different. If anything, I always say the later they walk and crawl the better, because once they do your life is quite different 😉
Here’s a link to our 5-7 mth physical development article, which might help too (and it addresses how babies vary and what might not be considered normal):
I completely agree with Dr. Jen – the baby comparing game can drive you crazy! Certainly every baby develops at their own pace as you can see from the developmental milestones A to Z article she linked. With that being said, when a baby has significant delays, I always recommend they be evaluated to make sure there are not other subtle delays. Perhaps you should schedule a visit with your pediatrician to discuss your child’s development. A simple physical exam can tell the pediatrician if your baby has normal muscle tone and a normal neurological exam, among many other things. If everything checks out ok, your mind will be at ease, and if the doctor has concerns, you can address any delays early on. Best of luck!