Sciatica is a pain in the butt

..literally! I'm not sure if this has been triggered buy my increase in weight, my poor posture (at times) or the fact that Junior is getting bigger and lying in a funny position - or all of these things! What I am sure of is it can be fine some times and agony at others...and it's a bit frustrating 'cos there is little I can do about it! Any tips warmly received! :)