Pulsating lower back pain

Hey ladies I'm 15 weeks and did some moderate lifting and bending today and began to have lower back pain (have had it on and off for 2 weeks now) except today it started pulsating on my lower back and so I called the dr because I never felt this before. Dr asked me to come in tomorrow and now I'm worried! Anyone else experience this and turned out to be just back pain or sciatica?!