Hi- not sure if this helps- but had some really bad lower back pain a couple of weeks ago- am now 8 weeks so around the 6 week mark I guess. Don't normally get back pain- so thought that it must have been due to pregnancy. I used a wheat bag- heated in the microwave off and on (cos your not meant to have too much heat when pregnant) and I found that helped. Lasted for a few days- but nothing since then.
Hopefully- might be this way for you as well. If this doesn't work go the panadol.
At least its the weekend so take it easy!