I have this really intense pain about half way down my back, centralised in the middle section and wont go away!! What could it be??

I havent had a very good night sleep so far. Its fairly hot over in perth and I had a bad migraine so decided it was best to have a panadine forte and go to sleep. And about 20 mins ago I got woken up by this intense pain around my spine. It was realy bad laying down, but now sitting up straight it is going away...

What could this be from? Maybe a bad reaction from the panadine forte?? First time I have had one while being pg. I had an appt with m/w today and everything was OK, I hope everything still is OK.....