My dd was doing the comando crawl at 7 1/2 months and she just began actually crawling at 8 months and a few days
I too was beginning to think that it wouldn't happen. Your little one was born the end of October so I wouldn't be worried about it at all at this point!!! Enjoy the lack of mobility- it is a wild ride when they can move around on their own, LOL.
Edited:
Sorry, I didn't see that he was 8 months old!! I still wouldn't be worried! A girl in dd's play group (not exposed to anything in utero) just began crawiling at 11 months. They all have their own schedules!