very upset and confused :( please read I need opinions :( and somebody to talk to

so last night I went to the er due to spotting but no cramping I spot everyday since I found out I was pregnant which was feb 18 that I found out and feb 23 I went to a obgyn to confirm and the lady made my first prenatal appt April 13. so I went and got a ultrasound a vaginal ultrasound and the lady comes back and tells me that the baby is smaller than she expected according to my lmp which was jan18-24 I should be 11 weeks and the baby measured at 6 weeks and 3 days and she told me she couldn't hear no heartbeat and that I have a multiple septations sac what does that mean .. I am only 18 years old. also the er told me that I have a threatened miscarriage but my hcg levels are really high they are 11,985 soo :/