How do I get my son to talk more?

He will be 1 on the 15th. Before he started walking he would say dada, baba, gaga (grandma) and sometimes mama. He started walking at like 9.5 months but since then, he won't say words anymore. I have always tried to get him to wave hi or bye but he won't do or say it. He never points at the things he wants. Just looks at them and groans then gets stiff. He understands the words we say. He will give you a high five but hardly even gives hugs and kisses.

A few things to note is that I'm a SAHM and he is the only child so far. I am pregnant with another boy.

He does play alone well and doesn't mind playing with me but would rather play alone. He still puts everything in his mouth. He enjoys playing with his toys and talking to them but nothing like saying words.

He responds to his name 70% of the time. When he is sleepy he really doesn't respond at all and he does give great eye contact. He laughs and claps and will engage with you but just refuses to repeat what you say.

I don't think he has autism spectrum disorder but I really would have no clue. Any tips or advice would be helpful.