1st ultrasound possible ectopic pregnancy?

Hi all- 1st pregnancy 5w 4 d and have Ulcerative colitis.  I have been having terrible constipation and difficulty with urination. Cramping pain waking me in the night and resolving once I go. All mainly left Side. Doctor brought me in after some spotting concerns. Says I am measuring more like 4w 6 days (3mm). Found gestational sac today, but nothing more. He said I should "assume" an ectopic pregnancy. Unable to tell if gestational sac is in or outside the uterus with today's ultra sound. (Didn't show me today's images) Doing blood levels today and Wednesday and another ultrasound in 2 weeks.  Anyone else gone through this and what was the outcome?