Maybe see a physio? I saw one for a few weeks last month for my lower back and hip pain and OMG it was good.

You could always try pelvic tilts standing against the wall. Otherwise I do these exercises...
* cat stretch - on all fours, tuck your tailbone under and draw your chin to chest curving your back upwards, then reverse it tailbone, drop your belly, lift your chin up...I get a nice flowing motion which helps loosen me up

* dog tail - on all fours again, move your left hip out and turn your head around to the left to look behind you and do the same on the right side...like a dog chasing its tail..

* on all fours (again!) and reach your right arm under your body as far as comfortable reaching out to the other side of the room, you can rest your shoulder on the floor/bed and you'll feel a nice stretch along the top of the hips/lower back...do the same with the left arm

I tend to do these when i wake up and before I get out of bed, which is when my back is the sorest and it helps loosen things up and then I have the nice hot shower, makes everything more bearable during the day.

HTH