8 months old seems too young for any of that stuff except rolling. I think they don't use crawling as a milestone anymore because kids do it at such different times. My daughter crawled really late - well after 8 months. My assumption was that she was either too fat or didn't have any reason to crawl. She started walking at exactly 12 months, talked early and well and hasn't had any issues. She just didn't crawl for awhile.
Maybe your baby is just really chill?

Definitely tell the doctor what you're worrying about, but I wouldn't lose a ton of sleep at this point.