I had these problems too (once again we seem to have had similar probs).  I went to a physio who gave me exercises. They were pretty minor exercises, like lying on my back with my knees bent, then pulling in my tummy muscles and lifting one leg up without rocking my pelvis etc.   I found that  they helped as did making sure I wasnt bending too much putting TOm in and out of his cot (he was at the lower stage of his cot when I finally did something about it so we ended up putting his cot on 2 piles....highly recommend that).  Jody would be at basinett height but if thats a little low for you put her bassinet or cot on soemthing to make it higher....we spend a lot of time bending just a little.  Also try to pull you abs in when you bend (easier said then done when you arent sure they even exist anymore)

My back got better but I still find I cant bend too much without having probs.  I think I have just learnt to do things more sensibly