Girls, hi! What does a baby do when they want to crawl? My son (3.5 mo…

Girls, hi! What does a baby do when they want to crawl? My son (3.5 months) started rolling over at the end of the second month, but only from his back to his belly and only with his right side. Now he's been trying to lift his bottom and push himself forward for two weeks, but crawling isn't working because he doesn't help himself with his hand and he lowers his head on the floor instead. When will he crawl if he tries like that? (He just starts crying when it doesn't work and sometimes even has a tantrum). Is this normal? When lying on me, he can reach from his belly to his neck easily. He's already not strong enough constantly