15 wks, hellish back pain

Jen
Help! I'm 15 wks and 4 days and I have been having really bad lower back pain. It is worse after sitting at work for the day, but it is pretty much always present. I get up freuently to take walks, try to sit with my legs planted on the ground, but it is not helping enough. The only thing that alleviates the pain a bit is lying down, which isn't an option at work. 
Are any of you experiencing this? How have you managed the pain? Do I need to go to the doctor? Chiropractor? Acupuncturist? 
I've had bad lower back pain before pregnancy, and the only thing that really helped was going on a low dose of an anti-anxiety med (lexapro). I went off the meds when we got pregnant. 
Your advice would be so much appreciated. Thanks!!