Terrible two's for sure! I did pick up on this however...
When is your baby due? You said you were pregnant in the "A little about me" section.
My three older children are mine biologically. The two oldest are 10 months and 4 days apart from each other in age.
My oldest daughter was too young to take on any "opinion" of Mommy having another baby when I was pregnant with my son, but my son was 2 when I was pregnant with my third (his sister).
It seems that the terrible two's accelerated with him more so than with his older sister who was 3 at this point.
Just as you described in your post, my son would do the same. It was half way through the pregnancy that I started catching on that half of what he was doing wasn't so much a normal act out of being 2, but it was more of a "Is Mommy still mine" type of behavior. But to confuse one more, he was still trying to be the "big boy".
Children can be challenging - that is a given. Understanding them is not always an option.
Be calm, loving, guiding, and and gentle. Talk, don't yell.
He's 2 years old. Give him a choice on Apple Juice or Juicy Juice for a drink. Give him simple choices for his age...but not for all subjects. If he's acting out, try this as it worked with my kids.
Whining and acting out would call for a "feel better rest"(what I called it to my children) and I would lie down with him on the bed. We would lay there and I would just stroke his hair on his head and talk softly. If he pushed my hand away, I'd just lay there and either sing a little song or pick up a book (kid book) and start reading quietly. Without fail, he'd settle down and listen to the song or get droopy from the hair stroking, or he'd get really insistent that I READ that book to him. Not always but more than not, he'd fall asleep and take a nap or a cat nap that left him refreshed.
Most of all.... I never forgot to tell him or any of his siblings when we went through these phases that I loved him.
Even in the most "souring" of moments when you want to pull your hair out.... step back and tell them that you love them.
You will survive this and so will your son. My children are now 17, 16, 14, 11 and 10.
This too shall pass. Good Luck (Big Hugs)