Could my son be autistic?

So me and my partner have recently noticed several things about our son (21months old) and are just looking for other parents opinions or general help from their experience.  

The most two obvious things we noticed is he doesn't respond to his name . However will respond if we say chocolate or something else he likes, but very rarely to his own name . His speech seems to have got worse over the last 4/ months aswell . The words he learnt mknths ago we cant get him to say alot of them anymore.  

I guess really we are just looking for any advice or past experiences to compare with. Are we doing the right thing when he doesn't respond to his name and we keep saying it over and over ? Should we seek help from the doctor?  

Any reply would be greatly appreciated . 

Thankyou