Hello. My son is now 20 weeks old and had the same problem at the same age. He would stand up next to the couch and sit up just fine, but no crawling and he screamed whenever we put him on his stomach! He started to crawl at about 10 1/2 months, and then bam! he was walking at 11 months! It was like, he just didn't want to have to do the crawl thing, so he only did it for about 2 weeks. I have no doubt that your little one will start to crawl soon enough. As you said, it's not a big deal, but it would be nice to see the progress. Just give him time and keep on with the floor activities and don't stress. He can probably sense your stress! Good luck :)