Rough toddlers

Br
I have a 5 year old son and a 3 year old daughter whose very rough but also very clingy towards me. I have explained to them that they will be having a baby sister or brother soon and I also explained the baby's current situation but sometimes they scare me. Last night after a big meal I stretched across the sofa to watch a movie and they both jumped on me and proceeded to elbow me and roll all over my belly. I am very fragile in that area, I'm not really showing. My kids are rough with a very short attention span so their very forgetful. Im afraid they will hurt me one day lbs. I have to nip this in a bud now. Is anyone else experiencing this?