Donut cushions tend to add a but of pressure to the area as well, get yourself something called a “Coccyx cushion”, its like a seat shaped like a butt, but with a small cut-out at the top, you sit it over that and it does wonders, way more comfortable than a donut
I'm 32 weeks as well for the tailbone pain I go to a chiropractor twice month since my body is going out of alignment due to the baby , which helps a lot. I also bought a seat cushion from Amazon for work. https://www.amazon.com/dp/B01KG6RX3O?ref=yo_pop_ma_swf