Need my priority seat.

Hey Mummies, I'm 19wks 5days preg. My belly looks huge now and I walk like a penguin🐧. I commute to work by MRT. There are days I wore like loose clothing and I understand that why people don't give up their seat but when I wore super tight clothes that stick to the body which can see my belly bump. I'm quite surprised people don't give up their seats despite me rubbing my belly like obviously🤰🏽, i notice they were looking but their eyes are glued back on their phone. I cant stand too long otherwise I'll get like bits of cramps here and there on my lower belly. How should I ask for a priority seat? What if they don't want to give seats. I don't want to face like embarrassing moments etc. Or even get myself video by some random strangers n em' posting it online. Help 🥲