so frustrated..

I'm trying not to over think it, but my daughter is 8 months and still not crawling. She will scoot and try to pull herself up, but she just won't crawl. She will get up and rock back and forth and then when I stick a toy out in front of her, she will go back to her belly and stretch out to get it instead of trying to crawl. 
I know every baby is different, but is there some way to help her crawl or get going?