twisting body...

OK I've been playing bass for around a year now - I'm happy with my progress but I haven't ever seen a teacher and I guess there's a few really basic things I'm still missing. So apologies if this is a very stupid/common question but hey, gotta ask these things at some point!

I'm having a problem where I tend to find my body twisting a bit while I play. Probably more noticeable when I'm standing, but happens when I'm sitting too. It's only very slight, but after a while it starts to become uncomfortable, and although I haven't done any serious damage or anything yet it definitely feels like I shouldn't be doing it.

I think it's because the point of contact of the bass with my body is off centre - when I put it on centre it's more comfortable but it's difficult to play in that position because - the bass is just in an awkward position and gets in the way of the right arm.

Thanks for any help!