Legs problem. Blood test any requested.

Hi my baby is 2 years old . Weight is 12 kg. ( He was 10 kg in 1 year) . Height is 86 cm. Not gaining proper weight. Several cough cold repetition. And ear infections suffers each month since 1 year completed. He is walking and running easily. But most time he runs on toe and fingers. What is that problem. Another issue is that he sits w sitting . I think he is doing so for last 5-6 months. But now we can see his legs are not straight . And knee bone of both legs are much towards inside. And legs are bowed. What is that I haven't see my child for legs. Actually he walks fast some time he fell when he fell in to floor  position become w sitting shape. Need genuine advice. Blood test any requested .thanks attached pic of both legs