Sounds like Sciatic nerve... being pinched from the weight of the baby.

I had a very similar thing (even before I got pregnant). I would be fine one minute, then excrutiating pain the next - sometimes preventing me from walking.

I went to a physio who did a bit of manipulation... and gave me exercises to strengthen and align my core muscles. As soon as I did those exercises it would fix up. After a while I would lapse... and the pain would return.

If you are doing physio exercises and they are not helping - go back to see the physio (or ideally another one). Maybe you're not doing them correctly - or they're not the right exercises for the pain you are currently suffering.

My DD is at the end of the week -- not sure if that makes a difference or not.
your DD is WHAT at the end of the week..... due to birth?????????

If you are pregnant... then the hormones in your body will affect your muscles and nerves too. And the weight from the baby will put a huge pressure on your lower back area.

If you have a child... and you are carrying them around... that will throw your hips. Best to carry your child at the front of your body, rather then on a hip. And if you put them on your hip - swap sides regularly... don't hold them on the one side all the time.