I need help with my 2 year old

We just found out a few days ago that I am pregnant with baby #3. We told out oldest ( he is 5) but We haven’t told our 2 year old because I’m pretty sure he won’t register the information like his brother will. But in the past week or so he has taken a huge interest in jumping and climbing on me. I have never liked it and I always make him stop. And now I feel like he is doing it more and more since I’m pregnant. Has anyone had this issue?? His main focus is around my stomach. My fiancé try’s to help keep him off of me but CJ is sometimes to fast for either of us.