My 10 month- almost 11 month old is not crawling. He also doesn’t get into a sitting position by himself. He can sit by himself if I put him on that position, but will always get out of it to just play with toys on his back. He can army crawl to get places, but mostly just rolls everywhere. He is also not trying to pull himself up to stand or walking along furniture. Should I be worried and seek help or does he just need more time?