Can't see baby in ultrasound

Danie • I`m 30, married, and have 3 kids, all girls.
I'm 7 weeks and 2 days and last week when I had my first appointment they couldn't see anything in the ultrasound but my hormones were still rising and today they still can't see anything and they said I might be having an ectopic pregnancy. Has anyone ever had this before? Also they want me to take a shot that would end my pregnancy. I've read a lot of women had then happen to them and by week 8 they saw the baby but my doctors are really pushing for me to get this shot. Can anyone help me or have any advise as to what you would do?