I think my son is autistic?

i have a 21 month old toddler. He is well developed in speech. However, lately he feels the need to babble. He will start saying dada and then it'll turn into dadadadada dadadada. He won't respond when i call his name. He doesn't ask for help. He doesn't understand how to interact with other kids. He enjoys banging his head on the floor and walls. I'm really worried. Are these signs of austism?