back pain!

Im a first time mum and 15weeks 5days pregnant, im a part time cleaner (6 hours a week) but my back is absolutely killing me, its so achy and sore, sometimes when i havent even been working. My partner gives me massages but sometimes its just too painful. Its my lower back just above my bum. Is this normal? Is there anything i can do to stop the pain? is it possible its the way im sleeping and i need to use a pregnancy pillow? (i havent really got a bump yet) or is it the pntosition baby is in? any advice is much appriciated!!!