Back pain early pregnancy

I'm around 6 weeks pregnant and my back is in absolute AGONY! I've woken up now in the early hours of the morning and had to go for a bath because I simply cannot lie in bed :( I was up the hospital last night with the problem as it was in my shoulders but was checked over and everything looks okay..  My bloods have doubled and other tests were normal so baby is doing well.. But I'm still getting pain in my lower back. It's really unbelievably painful!! :( has anyone got anything I can do to ease the pain? It's keeping me awake now.. I don't know it it's unrelated to the pregnancy but it's killing me! Any tips or advise would really help!! I'm a bit nervous to keep taking painkillers because they're not really recommended in early pregnancy.???? Thankyou!! Xxxxx ????