Too early?

So I have a history of an ectopic pregnancy in October of last year, so when hubby and I found out we were pregnant this month, the doctor wanted to rule out an ectopic right away. I went in for an ultrasound at 5 weeks and 3 days and saw only a gestational sac measuring 5 weeks and 2 days.

Doctor wasn’t worried about not seeing anything inside the sac yet, and asked me to come back weekly to see the progression of the baby.

Should I be worried about not seeing a yolk sac or could it be too early?

I’m feeling pregnancy symptoms like crazy, tender breasts, fatigue, twinges here and there, increase in watery CM, and right at the start of my 6 weeks....all day nausea lol.