8 months baby is not reaching for toys/cannot sit unaided

[Meryana]

My LO  will turn 8 months next week. he is not reaching for toys and generally seems to stuggle with using his hands/arms accurately (poor coordination) and cannot hold things up with his hand. He is just batting on things and can put some weight on his leg for a second and infrequently if he is in the baby walker. He cannot sit up independently at all, and even when he is supported he pushes himself to the back, he prefers lying back. he can roll over his tummy and push his leg to the back. can hold his head up when he is lying back or on his tummy. he chews his hands a lot. he can babble, says dada, baba, inga. His voice is loud. his eye contact is totally fine, can follow anything comes infront of his eye. his hearing is perfect. He has been eaten solid since he was 4 months. Please help as I am worrying a lot. The GP did not take any action , just says he is normal! he did not even do the physical examination for him!