I'm 28 Weeks Pregnant And Wondering What Is The Ball

I'm 28 Weeks pregnant and wondering what is the ball like sensation right below my breasts in the center towards my stomach area? It dosent hurt but it feels weird when I'm sitting so I lay on my side. It's not painful but it dose feel weird and slightly discomforting and I can still feel the sensation while laying on my side but not as much. Almost like a pushing or pull sensation that's constant. Like someone put a heavy ball on the center of my chest or in that area...