14 month old not walking/ crawling 😰

Hey girls, so I’ve tried googling and finding information about this topic but I seem to not be able to find little to nothing to answer my doubts and questions. My 14 month old is not walking and he just barely last month started scooting around to get to things. His ped doesn’t really tell me much just that if he’s not walking by 15 months we’re going to start therapy. Also he’s not talking much just still babbling & he’s not as big as the other kids his age he’s pretty small & doesn’t gain weight fast (19 pounds) when I try to help him walk he starts crying & refuses to give steps unless he’s in his walker. When he was an infant he didn’t start smiling till abt 5/6 months in & just now he’s starting to chuckle. I’m just worried something is wrong with him & can’t help but feel useless. If anyone has any opinions or comments I would be more than thankful to hear them! Just a worried mommy trying to get opinions from other mommies❤️