Anyone else?

So according to my LMP(September 16th)

I should be 7 weeks 1 day. I was having some sharp zing type cramps last night so decided to go to the ER just in case.. they did an ultrasound and couldn't see anything. My bhcg was 180.

I should mention that my period lasted almost 2 weeks, and had a peak opk on October 4th.. is it possible that I ovulated later than "normal" && I'm earlier than 7 weeks? Or possibly ectopic?

Any thoughts are greatly appreciated. I'm seriously stressing.