Ectopic?

I'm 13 weeks and have been getting a really bad pain in my lower right abdomen. It doesn't happen every day and it's usually when I wake up and last for about half the day. Could I be this far along and be ectopic without knowing?? I've had all my prenatal blood work done and I've had 3 ultrasounds so far and everything was fine.

I don't know how they detect that kind of thing, can they tell if it's ectopic through ultrasound?

I'm hoping this is something minor like cramping or gas