naru89 is right, that's what I'm doing right now to ease a back ache and Braxton hicks it feels gooooood even if i am wedged into the world's tiniest bathtub and may need to call fire brigade to get me out haha
A warm bath is your best friend at 28 weeks it usually eases my braxtions
I never had Braxton hicks but i had back labor if you can sit in water like a pool or warm bath it helps relieve some of the pressure my water broke and I wasn't dilated at all hope it gets better!