Any ideas

How big is he? 

bout 48 pounds and 11 mths old and chew machine but smart as a whip (all parents say that) have a picture of his mother

I see Pit mix.  I don't think he has any Jack in him.  48lbs is pretty big.  The only thing that resembles jack is the placement of the markings, but Pits can have those markings as well.  A Jack would have to have been bred with a pretty big dog to reach 48lbs.  I'm going to stick with Pit mix.

see that scares me with he loving to put his mouth by my hand and a baby on the way. What is the best thing to do to stop it . I know this isnt the help section but just wondering

Just plain say "no mouthing" and take your hand away.  You also want to begin to teach "be gentle" -- that means 4-on-th-floor and no pushing, shoving, etc. 
 
When you start to 'feel life' let the dog in on it -- pregnancy is natural to them -- and you'll want to teach other concepts like "Help Mom" -- and "Wait" -- reward him for dropping his toys in a bucket - if you teach HIM to pick up after himself it's gonna be easier with the baby and it will also teach him HIS toys from your stuff. 
 
But "help" can mean "go with me out here because it's dark" or put a hand on his shoulders when you need to steady yourself getting up out of a chair.  But pushing him BEHIND you so you don't trip on him when your arms are full and saying "wait" (meaning I do this first BEFORE you do what you want) is a valuable command -- it can be diverse -- "wait" gets him to be patient while you do something BEFORE you let him out.  Just remind him when you DO complete what he wants/needs "Good boy! GOOD wait!!"
 
Call the nursery the 'baby's room" and pat your belly and say "Baby!" -- he'll get it. 
 
Good luck!!
 
BTW -- I see probably boxer/pit/and MAYBE beagle or basset.  Mostly, to be honest, I see MIX!!!  I see good old-fashioned "probably will be healthy because it's not ONE thing enough to get breed-related health problems"!! and probably a dog from "survivor" stock.  Good luck - I'll bet he'll be a great dog!!