Back pain relief recommendations?

Hi all - 37wks here and struggling with mid to right back pain that is also coming from the front ribs I think from baby kicking. Also- have slightly elevated fluid levels so might also been causing everything to squash. The pain is worse after walking more than 15 mins which sucks because I love walking. Any tips from anyone? Prefer not to take paracetamol regularly. And it’s not too bad at rest- but worse when I slouch, so trying to keep my posture straight. Anyone else had this issue? I guess it’s probably common- just quite irritating now as I’d love to do some longer walks in these last weeks!