Back pain so bad I can't stand??

I'm 18 weeks and having severe lower back ache so bad it's like throbbing and I can't even stand up for too long. Laying in bed on my side doesn't help either. It feels almost like i pulled something. It's hurt like this before but never this bad. I took Tylenol but don't want to be doing that every night. Ughhhh. I walked around not a ton but a considerable amount today could that be it? It hurts so bad. No cramping or spotting.