Pregnancy can cause back aches
Pregnancy brings many changes to the body. And a common complaint is back pain.
An article from About.com explains that the pain is caused by the hormone relaxin, along with changes to the pelvis and a shift in your center of gravity.
Fortunately, exercise (particularly pelvic tilts), watching your posture, and bending and lifting objects in an appropriate manner will help.
And don't worry, pregnancy doesn't last forever. It only seems that way.