D.B.
It's normal to be worried when you've had a major episode in the past. Pregnancy causes all kinds of pains, and you probably have some scar tissue from the previous surgery. Ectopic pregnancies usually cause shoulder pain as well - the phrenic nerve refers pain from the area around your Fallopian tubes up to the shoulder. If you don't have that, it's a good sign. A gestational sac in the uterus pretty much confirms that the pregnancy is where it should be. If you still have pain that concerns you, call your OB - they should have appointment slots for urgent care even if your regular appt isn't for 2 weeks. Don't go to the ER and stress yourself out (and rack up costs) unless it's truly a matter of an emergency. But DO call your OB and insist on an early appointment, describing your symptoms and reminding them of your previous trauma.
Good luck!