Possible Autism

My son is 22 months old and used to say a lot of words like mama, dada, hello, bye, shoe, ball, woah... But, has regressed in several ways. He now only says no, or uh oh maybe once a day, sometimes not even that. He stopped giving high fives to us, and will not play pick a boo anymore. His first word was BOO, and he won't even use it! When we take him to the mall play ground, he doesn't play with kids his age, he wanders off and does his own thing. But he plays well with his siblings. He likes to be chased, but cannot play a game of rolling ball back and forth. He takes the ball, and gives it to us, and wants us to throw it. Basically, just fetch! When he gets frustrated or upset, he hits his head with his hands and screams. He will not mimick us when we say words, and won't repeat things.. or even touch his nose, when we are trying to teach him eyes/ears/nose/mouth... when i tell him UP, he just looks at me..I repeat 3 times, and he just hugs me.. It is almost as if he doesn't understand what we say to him. Everytime he seems to not understand, he will hug us. He doesn't listen to things we say like simple commands of no, don't touch.. or where's the baby? Sometimes we are unsure he knows his name. There have been moments when he will not even hear us, but I have made tiny ssss sounds, and he'll look at me.. but two minutes before, me clapping and loudly calling his name, no response! I have even tried callign his siblings names, thinking he may be confused as to what his name is. Still, no response. I know it is not normal for a toddler to regress like he is... We are concerned he is autistic. His aunt did the same kind of regression at 2 years old. He also does not see the 'invisible line' when we point to something on hte other side of the room, he just looks at our finger. He also does NOT point at things either.