T.,
I agree, talk with your pediatrician. On the other hand though, I never crawled "normally". I was born 2 months premature 26 years ago. I crawled on an elbow, a hand, a hip, and a knee. If I remember what my dad told me it was right elbow, left hand, left hip, and right knee, or some type of variation of that. I'm fine now. Some babies only do the army low crawl, some babies do the traditional hands and knees.
If you are concerned, ask your pediatrician, it's always better to be safe than sorry.
Example: At my daughter's 10 month well baby check-up she still didn't have any teeth. I asked her pediatrician if I should be worried yet, she said not yet, but if she doesn't have any teeth by 13 months I would have to call and make an appointment. She just turned 11 months yesterday, and is about to cut her first teeth. SO now I don't have to worry/wonder.
Anyway,
Hope this helps,
Melissa