hey Ashlea

it could be sciatic pain...but this tends to be a sharper pain that shoots down the legs from the buttock...so the reason I think it may be is the position you descirbe that provides some relief

the pelvis is also in a phase of 'relaxing' which will further enhance the sensation

its hard to know for sure what it is...sorry hun

but I would recommend having a chat with a physio, chiro or (of course) a good pregnancy yoga teacher to see what they would recommend

I have a yoga pose on my pregnancy yoga page (for you to try) that would provide relief

hope this helps

xx yogababy