Back pain is common pregnancy symptom. Added weight to your body from the growing baby and uterus, placenta, more fluid in your body. Could be your sleeping position too... do you sleep on your back? It is best to sleep on your side during pregnancy especially now that we are all getting closer to due date. Either try sleeping with a pillow between your knees or you can get a pregnancy pillow and use that. Doing a few stretches before you go to bed at night might help also. Lookup some pregnancy exercises if you aren't sure or talk to a personal trainer.
Hi I'm now 25 +1 and 2/3 weeks ago I had back ache to the point where I got stuck on the sofa unable to get up.. the only change I made was a slept with a pregnancy pillow (more so for the cushion in between the knees) for support.. it took 3/4 days but slowly my back improved!! I don't look back now and when away for week ends the pillow comes too! I came up with the fact I was sleeping (like the recovering position) twisting the base of the spin.. putting pressure on the bones and muscles.. I'm not saying this is what your issue is but if you have a spare pillow.. it's worth giving it ago!! Good luck!!