I think she's sitting low?

So I'm only 18 weeks and 4 days, this is my first pregnancy but the past two or three days I've started to experience some pretty bad lower back pain, and quite a bit of discomfort down lower. I have started to feel her moving and what not but I also feel her pretty low, sometimes not even above my panty line. Is this normal? I mean I know the lower back pain is a well known symptom and what not, as well as the discomfort, but this early? Thank you in advance.