Hi A.,
Crying a lot is pretty normal for a 4 year old - especially one who can see his life is about to change. Try to put yourself in his shoes. He's been the center of your life till now, right?
Rather than saying, "Mommy won't talk to you..." etc - try giving him a hug and saying, "Do you need some help?"
While you want to be consistent with helping him continue to do things he needs to learn like eating healthy or putting away his shoes, he may just need a little comfort right now. If you give him some, you'll probably find he'll soon recover from this habit very quickly.
Blessings on you and yours as you await the arrival of your new baby!