Sharp pain right side

I'm 4 weeks, 6 days pregnant. Early this morning I experienced severe stitch like pain on middle right side. I ended up going to the hospital because after a previous ectopic on the left I was so scared about having another one. Turns out a little sac is visible in my uterus so it has implanted in the right spot. Still not sure what this cramping pain was though. Maybe ligament pain?? Anyone else experienced this?