Hello!
I was literally in your exact same situation 2.5 years ago! I was home with a 20-month-old son (bright, active, spirited) and 4 months pregnant with the next. My husband has to be amongst the world's best men/fathers/husbands and he brings in a very good salary at an incredibly stable job. Yet I would regularly find my son AND myself on the floor bawling at each other! He would just get SO upset and I would feel SO overwhelmed and guilty that I would end up calling my husband in tears begging him to come help! That left me feeling even MORE guilty and MORE inept at this whole parenting thing, and here I was having another child! I even went so far as to ask my son's pediatrician what was going wrong with him because he was just so needy and moody. How on earth could I get dishes done or dinner made with a child like him?
If someone could have just shown me what my life would look like 6 months from that moment, it would have helped a LOT. Apparently the "terrible twos" start at 18 months most of the time. And while there are a lot of things to love about that age (which I appreciated the second time around with my daughter!), there are a LOT of challenges. You are hitting that really tough age right as your body heads into your 2nd trimester and you and your son are both so busy going through your own body's turmoil that it's really hard for you to understand each other. While you obviously need to play with him and meet his basic needs, my advice would be to just back off the guilt and realize that in a few months, things WILL be okay.
It seems like the second my son turned 2 and got a little sibling a few weeks later, he totally mellowed out. He was done with whatever developmental stage he was going through that caused him to totally freak out 50 times a day and he was absolutely delighted with his new sister! He truly wasn't jealous and having her around and all the things he could do to "help" (get diaper, blanket, pick up her toy for her) made him feel really big and helpful! He totally thrived on it and suddenly the whole mom thing just "clicked" and I realized that it really was going to be okay.
I know that every mom and child are different, but I've seen this same thing happen to several friends as well, so I'm hoping that you can just steer yourself and your son through this time and then come out on the other side intact!