airline seats and my coccyx

i hope this is allowed. i *love* airline travel, but have a strange problem. my butt hurts! it happens whether i’m in coach/premium/first. usually about two hours in, a dull ache has built to pain, and i start shifting my position from hip to hip, which helps a bit, but must be annoying to those around me. i have a fluffy build, but it’s all chest and belly with no butt. has anyone had a similar issue and found an easily-packable solution? tia